just putting this
up here fro some of those still testing and tweaking
their suspension for the upcoming season for road racing
or just tring to get a good ride. for some of you all it
may be general info you already know as for the rest you
may just be getting into suspension and dont know some
of the basics. either way its a learner or
refresher.
Spring Rate Changes (def.
important for those who dont pay att. to
this) Modification - Effect on Suspension
Increase front and rear rate - Ride harshness
increases; tires may not follow bumps causing reduced
traction. Roll resistance increases.
Increase
front rate only - Front ride rate increases. Front roll
resistance increases, increasing understeer or reducing
oversteer.
Increase rear rate only - Rear ride
rate increases. Rear roll resistance increases,
increasing oversteer or reducing understeer.
Decrease front and rear rate - Ride harshness
decreases; tires follow bumps more effectively, possibly
improving traction. Roll resistance decreases.
Decrease front rate only - Front ride rate
decreases. Front roll resistance decreases, decreasing
understeer or increasing oversteer.
Decrease
rear rate only - Rear ride rate decreases. Rear roll
resistance decreases, decreasing oversteer or increasing
understeer.
Antiroll Bar Changes (aka sway
bar) Modification - Effect on Suspension
Increase front rate - Front roll resistance
increases, increasing understeer or decreasing
oversteer. May also reduce camber change, allowing
better tire contact patch compliance with the road
surface, reducing understeer.
Increase rear rate
- Rear roll resistance increases, increasing oversteer
or decreasing understeer. On independent rear
suspensions, may also reduce camber change, allowing
better contact patch compliance with road surface,
reducing oversteer.
Decrease front rate - Front
roll resistance decreases, decreasing understeer or
increasing oversteer. More body roll could reduce tire
contact patch area, causing understeer.
Decrease
rear rate - Rear roll resistance decreases, decreasing
oversteer or increasing understeer. On independent rear
suspensions, more body roll could reduce tire contact
patch area, causing oversteer.
Shock
Absorber Changes (aka your struts) Modification -
Effect on Suspension
Increase rebound and bump
rates - Ride harshness increases.
Increase
rebound rates only - On bumps, tires may leave track
surface.
Increase bump rates only - Body roll
resisted; outside tire loaded too quickly; car won't
stabilize into a turn.
Decrease rebound and bump
rates - Ride harshness decreases; car may float over
bumps.
Decrease rebound rates only - On bumps,
tires follow track surface more effectively; car may
continue to oscillate after bumps.
Decrease bump
rates only - Body rolls quickly; car is slower to
respond to turn-in.
Troubleshooting Tire
Temperatures Reading - Handling problem - Reason
All tires too hot - * - Compound too soft for
track and ambient temperature conditions.
Front
tires too hot - Understeer - Front tire pressures too
low.
Rear tires too hot - Oversteer - Rear tire
pressures too low.
Inside edges too hot - Too
much body roll - Too much negative camber or too much
toe-out.
Outside edges too hot Too - much body
roll - Too little negative camber, too little toe-out or
too much toe-in or wheel width too narrow for tire
width.
Center of tread too hot - * -Tire
pressure too high.
Edges on too hot - * -Tire
pressure too low.
All tires too cold - * -
Compound too hard for track and ambient temperature
conditions or car not being driven to limit.
Front tires too cold - * - Inadequate load on
front tires.
Rear tires too cold - * -
Inadequate load on rear tires
Solving
Handling Problems Problem - Manifestation *Solutions
Steady state understeer - All turns or low-speed
turns only *If front tire temps are optimum and
rears are low, stiffen rear antiroll bar; *if front
temps are too hot, soften front (most likely). *If
front tire pressures are optimum, decrease rear tire
pressure. *Increase if chunking occurs. *Improper
front camber. *Too much body roll at front, causing
excessive camber change.
Steady state understeer
- High-speed turns only *If front tire temps are OK,
increase front downforce. *If front tire temps are
too hot, reduce rear downforce.
Steady state
oversteer - All turns or low-speed turns only *If
rear tire temps are optimum, with fronts too low,
stiffen front antiroll bar; *if rear temps are too
hot, soften rear antiroll bar (most likely). *If rear
tire pressures are optimum, decrease front tire
pressure. *Increase if chunking occurs. *Improper
rear camber.
Steady state oversteer - High-speed
turns only *If rear tire temps are OK, increase rear
downforce. *If rear tire temps are too hot, reduce
front downforce.
Corner entry understeer
*Front shocks are too soft in bump
resistance. *Too much front toe-in; use a small
amount of front toe-out.
Corner exit understeer
*Rear shocks are too soft in bump. *Front shocks
are too stiff in rebound.
Corner entry oversteer
*Rear shocks are too soft in rebound. *Rear ride
height is too high (too much rake) compared to front.
Corner exit oversteer *Rear shocks are too
soft in rebound. *Too much rear toe-in or any rear
toe-out.
Straightline instability *Tire
pressure is too low in one or more tires. *Too little
positive front caster. *Too much front toe-in or any
toe-out in rear.
Straightline speed too slow
*Too much overall downforce. *Too much toe-in or
toe-out. *Ride height is too hight.
Excessive
steering effort - All turns *Too much positive
caster. *Front tire pressures are too low.
Chassis or suspension bottoms *Spring rates
are too soft. *Shock absorber bump rates are too
soft. *Inadequate suspension travel. *Inadequate
ride height.
Re: Something you all can find useful in
your setu
When Shopping For
Wheels, Is Bigger Really Better?
The last few
years, the "touring car" look has gripped the streets,
with practically everyone and their brother slapping
huge rims and super-low-profile tires on their street
rides. These easy bolt-ons may help the car look a lot
cooler, but what does it do to performance and ride
quality? We wanted to find out.
The only way to
get a realistic answer to this question is to do some
tire testing ourselves, so we decided to take a popular
street car that originally came with 14-inch tires and
gradually increase tire and wheel diameter, measuring
performance and ride quality at each step. Our ally in
this test would be The Tire Rack, one of the largest
tire retailers in the free world.
The plan,
simply put, was to test a car on 14-, 15-, 16- and
17-inch tires to see what would happen. Would putting
17-inch tires on a car designed for 14s make it a bear
to drive? Would the smaller 14s be the
quickest?
Plus Sizing?
First off, our use
of the term "plus sizing" has nothing to do with large
clothes for women. In the automotive world, plus sizing
is all about increasing a car's wheel diameter while
decreasing the aspect ratio of the tire. This provides a
shorter sidewall height without affecting the overall
diameter of the tire.
An example of a plus-one
fitment is switching from a 185/65-14 tire on a 14-inch
wheel, to a 195/55-15 tire on a 15-inch wheel. The wheel
diameter has gone up by an inch, the tire's sidewall
gets a little shorter, and the since the overall
diameter of the tire remains about the same, the car's
gearing and speedometer reading don't change.
For
those of you unfamiliar with tire size nomenclature, on
a 185/65-14 tire, the 185 represents the width of the
tire in millimeters, the 65 is the aspect ratio (the
lower the number, the lower the "profile" of the tire),
and 14 is the diameter of the wheel in
inches.
Increasing the wheel diameter two inches
over stock--going up from the 14-inch rim to a 16-inch
rim and corresponding 205/45-16 tire--is an example of a
plus-two fitment. As you can probably guess, increasing
the wheel size three inches over stock would be a
plus-three fitment. Plus-four, anybody?
Why would
you want to put bigger wheels and lower-profile tires on
your car? In theory, the car's handling will improve,
since you're replacing some of the flexible rubber tire
sidewall with a metal wheel. Plus, most people will
agree that a car looks better when fitted with
low-profile tires on some nice, big wheels.
All
theories aside, will the car really handle better on the
extra-low-profile tires while still maintaining some
civility? That's what this test is all about.
Car
and Drivers
It's tough to test tires without a
car to mount them on and some people to drive it, so the
first thing we did was arrange a team of drivers. If our
tire test had a "star" driver, then that guy would be
22-year-old Brian Priebe.
Brian may not be the
most seasoned driver on the national autocross circuit,
but so far he has put together a resume that most
drivers would love to have: SCCA national championship
titles in both D Stock (1996) and Formula 125 (1997),
while at the 1998 Tire Rack Solo II National
Championship he finished second in F Stock to Dean Sapp
by just a few thousandths of a second. (In Brian's
defense, he had never driven that car before.) In 1999,
he took the C Stock national title in a Toyota MR2. He
also regularly instructs for the McKamey Autocross
School.
Longtime tire man John Rastetter would
also be one of our drivers. John serves as the Director
of Product Information Services for The Tire Rack, and
he been in this business since 1971. Not a tire guy who
just sits behind a desk, John has also been a regular
autocrosser for more than 30 years and organizes most of
The Tire Rack's driving demonstrations for their sales
force. He also has road raced with the Midwestern
Council of Sportscar Clubs and IMSA.
The Tire
Rack also loaned us two other test drivers, Michael
Jones and William Loring. Michael has been autocrossing
since the early '80s and now races a Dodge Neon ACR at
both Nationals and Neon Challenge events. In the winter
months, he ice races various Hondas and
Neons.
Fellow Tire Rack employee William Loring
also has an extensive autocross background, competing
since 1986. He currently runs a 1990 Civic Si in E
Stock, and with his previous car--a 1984 Civic 1500--won
a handful of regional championships.
Representing
the common man was David Wallens, managing editor of
Grassroots Motorsports. He hasn't won any national
titles of his own (yet), but has amassed enough seat
time in both autocross competition and testing to know a
pointer cone from a timing light.
Now that we had
a driving crew, we needed something to pedal around in.
We wanted a car that was popular and easy to drive at
the limit, yet nothing too boring. We hate to be vain,
but the car also had to photograph well--can't have any
junky-looking stuff spoiling our tire test article. Lee
Grimes, sales and tech manager at Koni North America,
came to the rescue, loaning us his personal 1998 Honda
Civic EX Coupe. (This testing was done just before the
release of the new Civic Si, by the way.)
Lee's
car pretty much represents what today's street
enthusiast is building: a late-model Honda that's been
tweaked with some bolt-on parts. An Ice-Man cold-air
intake and Genie stainless-steel exhaust system now help
the car breathe a bit better, while a Civic Type R
grille, dealer-optional lower lip spoiler and painted
rocker panels spice up the exterior. When it's not being
used for tire testing, the Civic wears 16x7-inch TSW
Alpine wheels and 205/45-16 Yokohama A520
tires.
The car is peppy and fun to drive, but
even Lee admits it's nowhere near as quick as the CRXs
he and his wife have campaigned in Improved Touring
racing. Still, the Grimes' Civic felt significantly
quicker than the last stock Civic EX we
drove.
Perhaps the biggest improvement on Lee's
Civic is the installation of Koni's new Threaded
Suspension Kit. Basically, it's a threaded coil-over kit
that's designed to be friendly to the daily driver.
These new kits, engineered by Koni Holland and Koni
Germany, include four Koni Sport-valved shocks (or
struts) fitted with threaded adjustable lower spring
perches and progressive-rate lowering springs. Most kits
allow between two and three inches of lowering, while
the threaded adjusters allow unlimited corner weighting
and adjustments. Kits are available for 1992 and up
Honda Civic, 1975-'84 VW Rabbit, 1985 and up VW Golf,
New Beetle, the front-drive Audi A4, and 1992 and up BMW
3 series. Development is under way for the Honda Accord,
Mazda Miata, Audi A4 Quattro and BMW M3. List prices are
between $1390 and $1990, although we hear actual street
prices will be less.
The car scored points right
off with our testers. "Great setup for road/street,"
said Brian. "I was impressed with how the car handled,
since I have spent some time in similar Civics with
Konis and R tires. In my opinion, this car would turn
times much quicker than a stock setup Civic with all the
shocks, tires, etc. The spring setup is worth every
dollar because it completely changes the handling of the
Civic.
"The new Civics are not fun to drive in
racing situations," he continued, "but Lee's Civic was a
blast. Every time I got out from behind the wheel, I was
having more and more fun with the car and astonished of
what it would do.
"If we would have adjusted the
rear more, I feel it could have been set a little better
for Solo, but that is the beauty of the adjustable
struts. I bet if the struts were adjusted down on the
road and up on the Solo, then the car would contain the
best of both worlds."
Fellow tester William
Loring also had a blast behind the wheel. "I was
certainly impressed with the way the Honda handled
itself on the track. We took well over 100 laps in this
little car, and it soaked it up without complaint. The
brakes never faded, and the motor always felt
fresh."
On the street, the car was certainly
stiffer than stock, and really only got uncomfortable on
roads with serious expansion gaps in the pavement. As
you'd expect, ride comfort was directly-proportional to
pavement smoothness.
Road and Track
Since
plus-size tire upgrades are extremely popular for both
street and track use, we intended to test the car in
both environments. Our street miles would be racked up
on Tire Rack's official Real World Road Ride loop, a
seven-mile path through South Bend, Ind.
The loop
samples a wide variety of surfaces and driving
conditions, including bumpy pock-marked roads, a smooth
highway, on-ramps and off-ramps, congested city streets
and curvy two-lane roads. As this loop uses all public
roads, no times were taken--we just wanted to see how
the different tires and wheels would affect ride quality
and real-world street manners.
For the
performance part of the equation, we had Tire Rack's
Performance Test Track Drive autocross site at our
disposal. This course is both fun to drive and provides
a good workout for the tires, as it contains a slalom,
skid pad, fast and slow corners and a quick
straightaway. Even though times were in the 30-second
range, the course still allowed everyone to fully gauge
the tires' performance.
Tires
You can't do
a tire test without tires, right? As Dunlop builds the
original-equipment tire for the Civic and offers all of
the plus sizes needed for our test (all within two
percent of the O.E. tire's overall diameter), they were
chosen as the tire brand of the day.
The stock
fitment for the Civic, the Dunlop SP 20 A/S Metric in a
P185/65SR14 size, would be used for the baseline test.
The 15-, 16- and 17-inch tires would come from Dunlop's
new SP Sport W-10 line of ultra-performance
tires.
"The SP 20 A/S Metric is an 'all-season'
passenger radial for imported cars and in addition to
Honda Civics is used as original equipment on Toyota
Tercels, Nissan Sentras and Mazda 626s," explained John
Rastetter. "As an original-equipment tire, the SP 20 A/S
Metric was designed to blend all-season traction with
low rolling resistance and relatively long tread
wear.
"On the outside, the SP 20 A/D Metric
features three circumferential grooves for water
drainage and relatively small, siped tread blocks to
help provide the biting edges needed to provide some
light snow traction.
"On the inside, the SP 20
A/S Metric features two steel belts and a polyester cord
carcass to blend long wear with good ride qualities. The
SP 20 A/S Metric tires are S-speed rated."
In
other words, the original-equipment piece is a pretty
okay, not awe-inspiring tire. However, these tires are
perfectly adequate: they're black and round, and they
help the car go down the road. The Dunlop SP Sport W-10
tires, on the other hand, are a slightly different
animal.
"The SP Sport W-10 is an ultra
high-performance 'summer' radial which Dunlop designed
to blend good looks with a bad attitude," John told us.
"This makes the SP Sport W-10 appropriate for
customizing today's sport coupes and sedans because they
provide a different look with a size lineup that
provides a range of plus-one, plus-two and plus-three
fitments. Depending on size, the SP Sport W-10 features
V- or W-speed ratings.
"On the outside, the SP
Sport W-10's wide tread features large blocks (to
enhance dry road traction and handling) that are aligned
in a 'waving' directional pattern (to help increase wet
traction and resist hydroplaning). Dunlop's 'Chaos'
tread block arrangement varies the size and shapes of
the tread blocks to help break up the repetitive
patterns and minimize noise levels.
"On the
inside, the SP Sport W-10 features two steel belts with
a spirally-wrapped JointLess Band (JLB) of nylon to
reinforce the tread area for high speed durability and
predictable handling while minimizing weight and
improving ride uniformity. The lower sidewall features
Dunlop's Max-Flange Shield (MFS) rim protectors to help
protect large-diameter wheels from painful curb
impacts."
Basically, the SP Sport W-10 tires are
right up there with today's crop of super-performance
street tires, the kind which offer better performance
than the race tires of only a few years ago.
To
help attach the tires to the car, appropriate wheels
were needed. Stock 14x5-inch steel wheels were used for
the original-equipment setup. These were both heavy
(19.2 pounds each) and a little boring to look at. When
testing the plus-size tires, aluminum wheels were used:
15x6.5-inch Kosei Racing Senekas and TRMotorsports
Typhoons in both 16x7-inch and 17x7-inch
sizes.
Testing, 1, 2, 3
We ran the street
part of the test first, with John, Brian and David each
running the test loop once on each set of tires. A
passenger always rode along to provide the driver with
someone to discuss the merits of each tire as well as
some company. A passenger also made sure the vehicle
weighed the same each time it went out. Each driver was
asked to always follow the exact same pattern, meaning
always use the same lane when more than one was
present.
All five test drivers ran the autocross
course, always in the same order. The Tire Rack test
course allows a flying start, which was followed by five
full laps. To help those of us not initially familiar
with the course get up to speed, a Lexus sedan was used
for practice runs. Some run times were thrown out due to
off-course excursions, massive cone executions, and
similar problems.
14-inch Tires
No one was
surprised by the fact that the 14-inch Dunlop SP 20 A/S
original-equipment tires offered the most comfortable
ride with the least road noise. However, even on the
test loop, their humble origins showed through. Brian
said the tires had a spongy feel while offering very
little personality. "Not very responsive on the road,"
he said.
When pushed to the limits on the
autocross track, the tire was easily overpowered and
failed to make any friends. Handling was mushy, the car
pushed every chance it got, and dipping into the
throttle quickly produced wheelspin. If the car drifted
off-line, bringing it back under control was
tough--riding it out was the only option. "Give it lots
of space," Mike said. "Its responsiveness was the
slowest of the group, and once it was at the limit, it
proved to be somewhat numb and unable to change the path
of the car," John said.
Brian quickly summed up
his feelings on the 14-inch tires: "Terrible turn-in,
terrible grip, terrible power-out." William agreed: "The
factory 14-inch wheels and tires had the loose, sloppy
feeling you'd expect from an inexpensive O.E. tire on a
narrow steel wheel."
15-inch
Tires
Swapping the original-equipment 14-inch
tires for the 15-inch performance Dunlops quickly made a
big difference in how the car went down the road.
Performance--and road noise--were both up.
"On
the road, the SP Sport W-10 in the plus-one P195/55R15
size confirmed you had changed from the all-season
passenger to the ultra high-performance summer tire
category," John said. "It was a little louder, harsher
and faster responding that the O.E. size."
Brian
found that the 15-inch tire "always felt planted to the
ground securely--firm, but not unbearable." He called it
a good dual-purpose tire in that it both performed and
drove well. On the down side, he also noted that tire
noise had increased.
On the autocross course, the
increased performance offered by the 15s quickly made us
forget the wallowy 14s, as William explains: "The move
to a wider 15-inch wheel and tire was a quantum jump,
providing much better transient response and far greater
confidence at the limit in addition to a big increase in
overall traction."
Brian also enjoyed
autocrossing on the 15s, and found the tire offered good
braking and good turn-in. Lateral grip was not great, he
said, although power could be easily applied when coming
off a turn.
John also preferred the handling of
the 15-inch setup, noting increases in steering response
and grip when compared to the 14-inch tire. "For that
matter, the handling balance of this combination felt
great on the Civic," he said. "The 55-series aspect
ratio of the tire--the tallest of the three plus
sizes--provided good turn-in and allowed the vehicle to
take a very neutral mid-corner set. This neutral balance
made the car responsive to the driver's input and made
making minor corrections relatively easy."
As for
lap times, the plus-one setup shaved an average of about
1 1/2 seconds off our times. Plus, the car also looked a
lot better.
16-inch Tires
"On the road,
the SP Sport W-10 in the plus-two 205/45R16 size was
just a bit louder, harsher and faster responding that
the plus-one size," John said. Brian agreed, also
pointing out how the tires seemed to make the most noise
over bumps and patches of mismatched pavement in the
roadway. I noticed the same thing. In straight-line
acceleration, the heavier 16s also felt a tad slower
than the 15s and 14s.
After pushing the 16s to
the limit on the autocross test course, John noted that
this plus-two setup offered a bit more steering response
and lateral grip than the 15s. "The handling balance of
this combination felt very good on the Civic as the
45-series aspect ratio of the tire provided a little
faster turn-in and maintained good mid-corner
stability."
The lower profile of the 45-series
tire also made it feel a little edgy, but no one really
complained. "Nothing to not like here," Mike pointed
out. "Gee, I thought the 15s felt good; these were
noticeably better."
Brian also preferred the
16-inch tires over the 15s. "Drives like the 15, but
every area is just better on the 16," he said.
"Comfortable in all aspects of performance
driving."
David also found the car a lot more
tossable and controllable on the 16-inch tires. Getting
the car back on line was also much easier, and on
average lap times were also slightly quicker compared to
the 14s and 15s.
17-inch Tires
As ride
quality had been dropping in proportion to aspect ratio,
we expected the 17s to ride worse than the 16s--but they
didn't. Not that either tire rode like the comfortable
O.E. radials, but both the 16s and 17s felt about the
same out on the seven-mile test loop. If anything, the
17s were a little quieter.
"The plus-three
215/40R17 size felt very much the same as the plus-two
size for real world ride, noise and handling," John
said. If anything, Brian found the 16s to be not quite
as harsh as the 17s.
The increased weight of the
17-inch setup seemed to hold back the Civic when
accelerating, but otherwise the car rode around town
quite well. Plus, the car seemed to turn the most heads
when fitted with the huge rims.
We all found
autocrossing on the 17s to be the most fun, as the tail
end of the car could be easily kicked around--never mind
that all other aspects of handling had been raised just
a bit.
"For the ultimate in grip and handling,
there is no doubt that the 17-inch setup was the
fastest," William said. "They had quick response in the
slalom and great holding power in the skidpad. However,
I felt they did require a little more attention from the
driver. There is an edge to these tires that is much
more sharply defined than it is in the smaller wheel
sizes."
Brian also found that the 17s had a
distinct edge. "I like this quality, but most people do
not. This is why I could turn the same times on the 16-
and 17-inch tires." Brian also felt that the 17s offered
the most lateral grip. Once again, increasing rim size
yielded slightly faster times for most of the
drivers.
Which Tire for You?
Seriously,
that's a question only you can answer, although all of
the drivers involved in the test had some
opinions.
"If money was no object, and I was
looking to turn the fastest possible lap times, then the
17-inch wheels would certainly be the way to go,"
William explained. "Being the low-budget racer that I
am, I like the 'bang for the buck' that you get with the
15-inch package. While they may not look as cool as the
bigger wheels, the tires will be cheaper when you wear
them out and the rims will be less prone to damage. The
16-inch package might also be a good compromise in this
regard."
Brian came away a big fan of the 17s.
"Looks the best of all of them and rides better or the
same as the 16-inch wheels. Why buy 16s? Just go with
the 17s." He added that running 15s in the North where
bumpy roads exist and 17s in the South where smooth
roads exist would be good advice.
John also
seemed to favor the big wheels, even wondering if they
held more potential. "If the suspension balance had been
tuned to the vehicle's wheel alignment, or a rear
sway-bar had been added, it would have allowed the lower
and wider plus-two and plus-three combinations to reach
their full potential and achieve even more
performance.
"The one area of improvement that
could not be felt or timed was the one that could be
seen," he continued. "it was almost surprising how much
each additional inch in rim diameter helped the lowered
Civic coupe complete its more aggressive visual
statement."
As someone who has always felt that
the added weight and increased rotational mass offered
by 16- and 17-inch rims were too much for a small car
like our test Civic, David came away very impressed by
the larger tires and wheels. Sure the 14s rode down the
highway the best, but they did nothing to inspire any
confidence on both the streets and autocross course.
Since all of the plus-size tires were detrimental to
ride quality, why not go with the ones that look the
best and offer the best handling?
Given enough time, most
enthusiasts can figure out how an anti-roll bar or a set
of brake pads will increase their car's performance, but
how many out there truly understand the benefits of a
good set of shock absorbers? Probably too few, which is
unfortunate. Properly selected and tuned, shocks can
make or break a car's foundation.
If you're one
of the masses who believe that a stiffer shock is always
the right way to increase performance and decrease lap
times, then read on. "Perceived stiffness cannot be
better by definition," explains Jay Morris, owner of the
racing shock company Advance Design and parent company
Ground Control. "Perceived stiffness would be a
misconception compared to actual stiffness, which should
benefit the race car.
"Why the distinction?
Because there is such thing as a perceived stiffness
that is not actually stiff. This is found in a shock
that is a poor design with internal leakage preventing
any real handling benefit, but which is very stiff over
bumps in a misguided attempt to improve handling. The
driver feels the bumps more, but the chassis is still
uncontrolled. This is usually the very worst handling
setup for any car."
What Do Shock Absorbers
Do?
Thanks to their common name, most people
think that shock absorbers absorb the shocks and bumps
experienced by the car as it travels down the road.
Technically, this is not true.
In reality, the
springs carry the load of the car and regulate the
suspension's reaction to any bumps or dips in the road.
They're the ones that really absorb the shocks. The
shock absorbers time the spring's reaction by changing
kinetic energy (the spring moving up and down) into
thermal energy (the heat built up as the shock's oil
passes through the various pistons and
valves).
"Springs hold the car," explains Lex
Carson of JRZ Suspension Systems. "Shocks control the
spring loading and unloading."
Since the shocks
are damping the springs, technically shock absorbers
should be called dampers. However, we'll stick with the
name shocks or shock absorbers, out of a matter of
habit. A strut is basically a shock that is also a
load-bearing member, but once again we'll stick with the
catch-all name of shocks.
To understand how a
shock works, picture a car driving down a road that is
perfectly flat except for one speed bump. If the car
simply has springs but no shocks, once the car passes
over the speed bump, the springs will continue to
oscillate until they disperse all of their kinetic
energy. As a result, the car will pitch and buck as it
drives away from the speed bump.
Now picture a
car with both springs and shocks encountering the same
speed bump. The springs would once again absorb the
bump, but this time the shock absorbers would damp the
spring's oscillations (by converting the kinetic energy
into heat), allowing the car to calmly drive away from
the bump.
Unfortunately, we all live in a world
filled with more than one bump. Our cars are constantly
encountering all sorts of bumps and dips. Throw in a few
turns and place the car in a competition or sporting
environment, and you can see how your suspension is
trying to do many things at once. This is why a good set
of shocks can make the difference.
Defining Our
Terms
Like anything in life, there is a certain
lingo used when talking about shocks-words like bump,
compression, rebound and extension. These words describe
the valving or action of the shock.
Bump (or
compression) is when the shock rod is compressed into
the shock body. Rebound (or extension) is when that rod
is extended from the shock body.
Note that the
same shock can have different bump and rebound
characteristics. You can have a shock that has a slow
bump (hard to compress) but a fast rebound (easy to
extend). Matching the bump and rebound characteristics
of a shock absorber to your car and venue is the trick.
Hopefully, we can help you here.
Who Needs Good
Shocks?
"Good shocks are probably the second most
significant handling change you can make to a stock
car," says autocross and road racing national champion
Jeff Altenburg, "tires with an alignment being the most
significant.
"The only car I competed in without
[upgraded] shocks was my 1989 Formula 350 Firebird," he
continues. "I ran one event in it at Jacksonville on an
undulating lot, and it was floating like crazy. I had a
set of hydraulic Konis for the next event which was the
Sebring Pro Solo 1991, and the difference was night and
day. I won the event and the Challenge."
While
some limited-production performance cars like the Miata
Sport and Camaro 1LE come from the factory with
high-quality shocks, most cars are sold with only
commercial-grade pieces.
"The average enthusiast
needs a good set of shocks because he is an enthusiast,"
explains Advanced Design's Jay Morris. "A difference in
handling and performance will neither be discovered or
cared about by a non-enthusiast, so why spend money?
This is the attitude (and usually correctly so) of the
car manufacturers, so the average stock or replacement
shock is engineered to be adequate, safe and inexpensive
as priorities over performance.
"This begs the
question of why can't a performance shock also be cheap?
It is not so obvious. The primary reason is that a
performance shock is both stiffer and simultaneously
accurately stiffer. With the increased stiffness comes a
requirement for less internal leakage, or bypass. For
the non-enthusiast, internal leakage is softer and
preferred.
"In an inexpensive shock, the
advantageous internal leakage inherent in using cheaper
parts (o-rings instead of actual piston wipers, for
instance) is utilized as part of the softer damping
characteristics desired by the non-enthusiast shock.
This puts the base cost below any performance shock,
because of the lower quality of parts reducing the need
for accurate tolerances. An economist could probably
work out an inverse exponential function to describe
this, but let's just say that it costs a lot
less."
Shocktek's Michael G. O'Callaghan further
explains the problems encountered by most street cars:
"Typically, when the shocks are at the end of their life
cycle, the rod seal will fail (hopefully slowly) and the
shock absorber fluid will leak out. The damping
characteristics of these aged shocks are not good: the
overall damping forces are much lower, the damping
curves have changed and there may be air in the shock
which may act like a spring. Bottom line: wheel hop,
uncontrolled porpoising, excessive body roll. Very
dangerous in a collision avoidance maneuver.
"A
lot of the readers of Grassroots Motorsports might be
changing the mission of a car, such as modifying the car
to be more competitive in a weekend autocross, or
installing stiffer springs, sways and shocks to make the
car corner better on the street," he continues. "In this
case, the idea of a 'good' shock is that it is very
important to match the components carefully when
modifying the suspension of a car.
"Not only does
the shock have to control wheel motion and body sway,"
explains O'Callaghan, "but it has an important influence
in controlling the dive and squat of the car during
braking and acceleration. And, of course, making sure
that the shocks remain functional is an important
preventative maintenance function that car owners should
perform on a regular basis."
Enthusiasts who
lower their cars-whether for looks or performance-also
need to considering upgraded shocks. In most cases, the
stock shocks will not properly operate when teamed with
short, stiffer springs. "OEM equipment is not meant to
be operated below stock height," explains Truechoice's
Greg Calhoun. "Another thing to keep in mind is that
when you lower a vehicle, travel is taken away from the
unit. If there is not enough travel, the unit has the
chance of bottoming out."
Those enthusiasts
involved in competition also need to think about their
vehicle's equipment and the effect those parts have on
their lap times. "A vehicle's performance is directly
related to the performance capabilities of its
equipment," explains Jim Arentz, design engineer for
Penske Racing Shocks. "When put to extreme conditions of
a racing environment, typically the stock equipment does
not provide the optimum handling package. Most road cars
are equipped to handle everyday driving over a variety
of road conditions.
"Racers need dampers that
will outperform the stock parts in extreme driving
conditions where comfort and ride aren't always a
priority. The handling becomes paramount as the control
of subtle variations in chassis platform movement and
bump recovery can amount to a large gain in lap
speed."
Charles Cadieux of Dynamic Suspensions
further explains. "A properly-sprung and damped vehicle
has a better chance of maximizing the tire contact
patch, therefore better grip, better turn in, braking,
acceleration, etc."
Are My Shocks
Shot?
So, how do you know when it's time for new
shocks? Even if your car came with better-than-average
shocks, they may be at the end of their
lifespan.
"Generally when your shocks are shot,
you will feel a lack of control or crispness in the
suspension," says JRZ's Lex Carson. "The car may begin
to bounce or float when you go over bumps or uneven
pavement changes."
"First, the car will feel
different on the track or on the road," continues
Michael O'Callahan. "It might be different steering
characteristics, different behavior over bumps or any
other anomaly. Next, visually check the shocks for
leaks. And finally, if you're still stumped, you can
always have the shocks dynoed."
Note than
sometimes you may have a spring problem and not a shock
problem. "Spring problems tend to be persistent and
consistent, shock problems tend to usually occur only in
transitions," explains Jay Morris. "Theoretically, if
you have a problem in the middle of a corner (shocks in
low-influence mode) it will be springs. Virtually any
other time can be shocks or springs."
Sometimes
you'll need to take the shocks off the car and inspect
them to determine if you have a problem. "A shock
problem is easily detected usually by hand-compressing a
damper off the car and comparing to another damper that
seems to be working correctly," explains Jim Arentz,
design engineer for Penske Racing Shocks. "The feel of
the damper as it's compressed, the speed at which the
shaft returns to an extended position, and the feel of
the adjusters are easy hints at problem areas. For the
best proof, a shock dynamometer usually can determine
the source of a problem instantaneously, whether caused
by system contamination, damaged parts, or an
incorrectly-built damper."
Also, note than an
on-track (or off-track) incident can also cause problems
with your shocks. "If the car has been involved in an
incident by hitting a wall, guardrail, or another car,
then it is best to at least have the shocks looked at,"
explains Greg Calhoun of Truechoice, Inc. "Most times
after a hit, the shock will need to be serviced
depending on how heavy the hit was."
You Get What
You Pay For
The first tough decision you must
face is deciding how much to spend. All of us have
budgets, all of us hate to lose, and all of us have to
balance the two. In all types of racing, you should buy
the best shocks you can afford. Inevitably, you'll
second-guess yourself many times and curse yourself for
not going to the next level. Hopefully you'll be able to
sell some of your first mistakes to your
competition.
Shock absorbers come in many sizes
and styles. They also vary in price from $25 each to
more than $2500 apiece. "The $100 shock doesn't have the
technology or the sophistication that a $1000 shock
has," explains Lex Carson. "It's like the difference
between an IT car and a WSC car."
Why the big
difference in prices? The high-dollar shocks have bigger
shock shafts, bigger pistons and bigger valve stacks.
They are also built with more care to tighter
tolerances. All of this costs more to manufacture. We're
not saying everyone needs to spend 10 grand on shocks,
but buying the best ones you can afford is usually the
smart move.
"Excluding a few glaring examples of
cheap shocks intentionally disguised as good shocks, you
get what you pay for," explains Advance Design's Jay
Morris. "Sometimes in performance, sometimes in
additional features, or if you spend enough,
both."
For example, Jay points out how a $199
Bilstein Sport shock for a Camaro offers good valving
and monotube quality, but no adjustment. That same $199
will also buy one Tokico Illumina, which has softer but
adjustable valving. However, a true race shock for that
Camaro that offers qualities found in both
shocks-rebuildable valving, monotube quality and
adjustable compression and rebound-will start at $399
each.
Where you buy the shocks and which company
you use should also be a factor. Shock tuner Guy Ankeny
of Ankeny Racing Enterprises says you should ask
yourself the following questions: "Does the person
you're purchasing shocks from know about the type of
racing you do-or want to do-with the car? Does the shop
have references for the types of shocks or shock work
that they're trying to sell? Can the person selling you
shocks give you any assistance in chassis
setup?"
Shocktek's Michael G. O'Callaghan also
notes that customer service should be strongly
considered when buying shocks. "Can you get decent
product support?" he asks. "Even the name-brand
manufacturers can get you lost in a maze of phone tag to
get even the simplest question answered."
Danny
Criss from Leda Suspension also recommends looking at
the quality of components and recommendations from other
customers. "Serviceability and initial cost play a role
as well," he explains. "Customers should be careful when
comparing different manufacturers' shocks and struts to
ensure that they are comparing apples with apples. A
good question that customers should ask themselves is,
'What kind of performance do I want, and what is the
budget?'"
Michael O'Callaghan also warns against
purchasing low-quality shocks. "Bargain performance
shocks can be very inconsistent in their damping
characteristics which you'll be able to feel very
easily," he says. "Brand name means nothing. Some of the
poorest-quality shocks are made by the biggest brands,
simply because their shocks are low priced. In fact,
some of the very expensive shocks have pretty poor
quality.
In response to the recent import
performance boom, many new shock companies have sprung
up on the scene. Some are truly geared towards the
performance enthusiast, while others are better suited
for common street use.
"When buying shocks,
especially lately, reputation is more important than
hype," explains Jay Morris. "Many companies have become
aware of the demand for quality suspension components
and have thrown their hats into the ring with
hastily-developed shocks.
"Paradoxically,
high-quality companies are left at the bus stop
regarding new customer perception (Bilstein). Even then,
there are so many inexperienced 'experts' in the
Internet chat rooms that a lot of misinformation is
being repeated as gospel. Try to get an opinion from
someone who has owned more than one
shock."
Options and Choices
Besides
quality and reputation, there are some nuts-and-bolts
options to consider that are well-suited for the
enthusiast. The ability to externally modify damping
characteristics is a desirable feature. If you can
easily tune your shocks to compensate for tire wear,
poor surface adhesion and sometimes even poor driving,
you'll be ahead of the game. Note than some shocks can
only have their rebound adjusted (single-adjustable
shocks), while some can have both rebound and
compression adjusted (double-adjustable
shocks).
"Double-adjustable shocks are geared to
the serious enthusiast who requires specific
ride/handling capability," explains Leda's Danny Criss.
"The single-adjustable units are simple and easy to
adjust and more than adequate for the average
guy."
As a driver moves up the ladder, then maybe
double-adjustable shocks should be considered. "At some
point in a driver's career, independently
double-adjustable shocks may be appropriate," says
Michael O'Callaghan. "Certainly in purpose-built race
cars at the higher levels, double- or even
triple-adjustable shocks are appropriate. However, they
are always more expensive and sometimes a lot more
expensive.
"From my observations, the average guy
at an SCCA event would not gain a significant advantage
from independently double-adjustable shocks. Those who
have them usually change the settings in the same
direction at the same time. (When they stiffen the
rebound, they also stiffen the compression.) This method
of adjustment can be done much more cheaply by a single
adjustment, double-acting shock or strut, in which the
rebound and compression are changed by the same
percentage by a single adjustment.
"Shocktek
sells both single- and double-adjustable shocks and
struts (based on Bilstein components), and the singles
outsell the doubles by a wide margin."
Penske's
Jim Arentz doesn't see double-adjustable shocks as so
confusing, however: "Double-adjustable shocks are easy
enough to understand (basically one bump adjuster and
one rebound) that the average enthusiast will be able to
understand with some experience and track
time."
When purchasing shocks, you should ask if
they are serviceable. Shocks comes in two basic flavors:
sealed and rebuildable. The rebuildable ones can be
repacked and tuned for your exact needs. The sealed ones
can only be thrown away when they wear out, and have no
potential of ever being upgraded. Of course, the
rebuildable shocks have a higher initial
cost.
"Konis are a very good off-the-shelf shock,
but can be a great shock when rebuilt to autocross or
road race specs," explains Guy Ankeny. During this
rebuilding process, changes are made to the valving so
the shock is better suited for its ultimate
use.
"Off-the-shelf shocks are best for the
average street enthusiast," says Truechoice's Greg
Calhoun. "When doing custom-valved shocks, the customer
is usually racing the vehicle in some form, whether it
be track events, autocross, or drag racing. When the
customer is in fact racing the vehicle, Truechoice will
discuss with them exactly what is being performed with
the vehicle and its setup to determine the proper
valving for their application.
"Custom valving
can also be performed to the standard street car,
depending on its setup. If the vehicle is lowered in
excess of 2 - 2 1/2 inches, it may be a case where the
shocks will need to be revalved and shortened. This is
necessary to allow for the increased spring rates and
sufficient suspension travel."
"Custom valved
shocks are for the discriminating enthusiast," says
Advance Design's Jay Morris. "When someone is
experienced enough to tell the difference in performance
and/or lap times, they should consider cost vs. benefit
of custom valving; often the price is worthwhile. Some
shocks are exclusively custom made, and although they
cost extra initially, there is no custom charge to be
paid.
"Please note that there are two types of
revalving: the limited revalving used to try to use a
street shock on a race car, and true revalving of a
purpose-built racing shock which optimizes compression
and rebound levels, rates of change and
limits."
Also note than several companies can
successfully convert a street shock to full-race specs,
installing the appropriate guts into a street shock
shell for production-based race cars.
All of
these better race shocks can be rebuilt or revalved at
factory-authorized facilities. Depending upon the brand
of shock and work performed, rebuilding and revalving
can cost $20 to $135.
Rebuildable shocks can also
be freshened to like-new condition at the end of the
racing season or before a major event. "Shocks should be
rebuilt at least every other year to keep them tip-top,"
says Guy Ankeny. "Fresh oil does make a
difference."
Even if the high-dollar shocks
totally shatter your piggy bank, you can still shop
wisely. "The very least anyone can expect to pay is to
find a mass-produced street shock that by coincidence or
substitution has sufficient damping for racing," Jay
Morris explains. "These shocks usually don't last as
long, and racing voids the warranty, but the
cost/benefit ratio is very favorable."
Damper
Designs
There are three basic designs of shock
absorbers: twin-tube hydraulic, twin-tube low-pressure
gas, and monotube high-pressure gas. Each of the three
has its own abilities and functions, and you will find
all three in street or street-derived racing
applications.
One of the most common
misconceptions is that a gas shock is filled entirely
with gas and no oil. In fact, all three designs use
hydraulic oil-they just may have a nitrogen gas charge
pressurizing the oil in the shock.
The twin-tube
hydraulic, as the name implies, has two cylinders (or
chambers) and no nitrogen. The inner cylinder is where
the rod and piston live and work, and the outer chamber
is a reservoir for oil and air. As the rod travels in
and out of the inner cylinder during stroking action, it
displaces oil from the inner to the outer cylinder, then
draws it back inside. Although this is the oldest of the
three designs, it still maintains certain benefits and
has a place in performance damping.
The twin-tube
low-pressure gas shock is much the same as the
hydraulic, except that it has a low-pressure nitrogen
charge (usually 5-15 bar/70-210 psi) in the outer
chamber, instead of the air pocket. Some manufacturers
seal the nitrogen in a plastic bag, while others will
allow the nitrogen in solution with the oil.
The
original theory behind placing the nitrogen inside was
that it would put the oil reservoir under pressure and
therefore raise the oil's boiling point, reducing the
tendency for heat-related fading or foaming as it passed
through the valves. That really isn't much of a concern
today as the quality of oil has increased in performance
dampers. Plus, modern performance shock design has moved
away from needle valves and o-ring seals that are
affected by heat and viscosity changes, and most street
cars and many race cars simply will not generate enough
heat to challenge the oil in a proper performance
shock.
However, when the nitrogen gas is in
solution with the oil, it can give the added effect of
damping really minute harmonics and motions that
otherwise would not be big enough to make the damper's
piston move.
The final design is the monotube
high-pressure gas shock. The monotube's entire body
serves as the chamber; this allows for a larger piston
area, and therefore it has the ability to transfer more
damping information over a smaller stroke area.
Displacement of oil by the incoming rod is handled by a
chamber at the bottom of the unit that contains a
high-pressure nitrogen charge (20+ bar/ 300+ psi) and is
separated from the oil by a floating piston.
Each
design offers certain advantages and disadvantages, so
the best choice will depend upon the intended
application.
A twin-tube design, when compared to
a monotube, has a longer stroke capability and greater
oil volume in a similarly-sized unit. Therefore, the
twin-tube will tend to give a smoother or more forgiving
ride characteristic and still supply the firmness for
proper handling control in vehicles that see average or
long suspension stroke length.
The larger piston
area of the monotube will give more control over much
shorter stroke lengths or at the lowest piston speeds,
but also tends to ride more harshly for exactly the same
reasons. In racing applications where heat generation is
more likely to be a factor, a monotube can cool itself
more quickly because the shock body is the wall of the
working cylinder.
You are likely to find
monotubes on non-production-based race cars (formula
cars and such), where control over very short strokes is
mandatory and ride quality is not an issue, or on
production-based race cars where once again control is
more important than ride quality. Most of the
rebuildable, high-end race shocks will use a monotube
design.
Note that gas pressure in the shock can
extend the oil's heat tolerances, but can also affect
ride height because the greater pressure can act as a
slight booster to the spring rate. Cars that run lower
spring rates don't want the boost, so they usually use
hydraulic shocks or must be willing to compensate for
the gas pressure.
Monotubes can also operate
while mounted on their side or at any angle, so they are
more conducive to racing pushrod suspensions, while twin
tubes must operate from upright to no more than 45
degrees from upright (which is still fine for most
production-based suspensions).
Before You
Call
So let's say you have decided what vendor to
go with and you have credit card in hand; now what do
you do? Before calling, Danny Criss from Leda recommends
you have at a minimum the following info on hand:
vehicle year, model and use (street, road race, rally,
autocross, etc.).
If the shocks are for a
competition car, he also recommends being aware of any
limitations set forth for that particular series. While
the general trend in racing has been a loosening of the
limits set on shocks, you're still better off knowing
what you can and cannot run before making any financial
commitments.
Retailers need to know the true use
of the car, stresses Jay Morris. "No Walter Mittys
allowed except for the Walter Mitty Challenge. No
retailer likes to field complaints from customers who
said they were going to go through drivers school and
never did." Morris adds one more caution for prospective
customers who may still be coming to grips with reality:
"We also need to know how much room you have left on
your credit cards."
If the car is a purpose-built
car (vs. a production-based race car), there is some
other info the shock builder will need, points out
Penske's Jim Arentz: "Make and year of car, type of
racing, inner spring diameter, spring length, needed
bump travel, fully extended length of existing damper on
car, number of adjustments desired, and type of chassis
mounts."
From the info you provide, the shock
company should be able to hook you up with the right
shock. "The tuner should be able to calculate natural
frequencies (or recommend spring rates) and a good guess
at the damping characteristics, while on the phone,"
explains Shocktek's Michael O'Callahan. "Note that this
information should not be a guess out of the blue, or
from 'experience,' but should be based on the physics of
automotive suspensions."
Rebuilding What You
Have
Many of us can't afford to buy new shocks,
but we would still like to improve our chances of
winning. Upgrading your present shocks may be an
economical way to vastly improve your car's transient
handling characteristics and bump control.
For
instance, if you bought off-the-shelf Konis or
Bilsteins, you can have the internal valving modified so
that it reacts more quickly or offers more resistance in
bump or rebound. Koni shocks that initially came with
only adjustable rebound can be upgraded to
double-adjustable specs (both adjustable rebound and
bump). Likewise, Shocktek can convert non-adjustable
Bilsteins to either single- or double-adjustable
specs.
This can be done at a substantial savings
when compared to purchasing new shocks. At the time of
the upgrade, you could also have the valving modified to
suit your specific type of racing. Autocross shocks
would be valved differently than road race or drag
shocks.
Having your shocks upgraded is good, but
just as in purchasing, be cautious. This work should be
done by factory-trained personnel (that has access to a
shock dyno), and hopefully by someone who also
understands the type of racing you do. Look for
references and look for the reputation the company has
within your racing circles.
Tuning for
Sport
Guy Ankeny offers the following advice for
tuning shocks for road race and autocross
competition:
Now that you've bought new shocks,
or had your old ones upgraded, how do you adjust them?
Well, the best way to adjust them is to test them.
Notice that I recommended "test" and not "race."
Hopefully you have a favorite test spot local to your
home. Test and tune days at your local track work
great.
Most shock manufactures will recommend
starting with the adjusters in the middle position so
you can work towards the extremes of shock valving. Now,
with your shocks adjusted to the middle position, head
out on track. While driving the car, try to analyze
exactly what it's doing, concentrating on corner entry,
corner exit and transitions.
For instance, if
your car starts to rotate the instant you turn the wheel
(you have to immediately counter-steer), there are two
basic adjustments to make: stiffen the front rebound or
soften the rear rebound. Either of these two adjustments
will slow down initial turn-in. Generally, keep
adjusting until the car starts to push, then back it off
until it feels right. Also, try to adjust one end of the
car at a time, so you can feel the difference each step
makes.
If you turn the steering wheel and your
car doesn't do much of anything, again, your shocks can
save you. This situation isn't very desirable, so here's
what to try first: Soften the rebound on the front
shocks and/or stiffen the rebound on the rear shocks. As
in the first example, adjust one end of the car at a
time.
Compression damping adjustments to your
shocks are handled slightly differently. Somewhere in
your race track or test area there's probably a
medium-sized dip that you'll need to become acquainted
with. This dip will help tell you how much compression
to dial into your shocks.
First, drive through
the dip at a medium speed with the shocks at a medium
setting. If your car crashes into the bump stops, please
don't repeat the procedure. Stop and adjust your shocks
for more compression damping before hitting the dip
again.
Now, retest the procedure, running through
the dip and observing what it actually feels like. Was
the dip absorbed by the suspension? If it was, I'd try
to stiffen the shocks a little further until I didn't
like what happened.
You definitely need to take
notes during the tests, so that at your next event you
can precisely adjust your shocks without having to rely
on your memory.
The key to suspension tuning is
balance. The car must be balanced to optimize the
driver's ability. A balanced car is easier to drive and
rewards the driver with consistency. That consistency
builds confidence. Don't be afraid to test and seek the
limits of your shock's ability-this in itself builds
confidence.
Sometimes testing may seem to be
getting you nowhere. When that happens, if you can
retrace your steps, most of the time the "light" will
reappear. (And hopefully that light is not an oncoming
train.) You then realize you've made a silly mistake,
which needs to be corrected.
If that light
doesn't turn on, call the people who sold you the
shocks, or contact your rebuild facility. This is why
it's important to buy shocks or rebuild services from
people who know what they're doing. Unless they can
really assist you with adjustments, and not just read
from a manual, you are up the creek-with no
paddles.
Advice for the Drag
Enthusiast
Five years ago, few if any people were
drag racing front-wheel-drive cars. Now, it's one of the
biggest rages in motorsports, with literally tons of
Hondas and Nissan making weekly trips to the drag strip.
These days, it's not unusual to see these cars solidly
in the 12- and 13-second brackets, territory once owned
by V8-powered machines. (The top Hondas are knocking on
the door to the nine-second club.)
While drag
racing provides some interesting technical hurdles for
any kind of machine, front-drive cars in particular face
a battery of problems. The biggest obstacle faced by
front-drive drag cars is rearward weight
transfer.
As soon as the driver jump on gas, the
car's weight quickly transfers away from the front
wheels and towards the rears. In a rear-drive car, this
weight transfer only helps the car launch out of the
hole. However, rearward weight transfer does nothing
positive for a car whose front wheels are doing all of
the work. Stomp on the gas and the drive wheels are left
unloaded, allowed to turn horsepower into
smoke.
While many people simply throw more and
more power at the situation, a smarter alternative
exists: tuning with shock absorbers. By keeping the
weight up front, traction can be increased and
quarter-mile times can be cut down.
For some more
insight on this topic, we posed some questions to GRM
regular Lee Grimes, sales manager for Koni.
Q:
When setting up a front-drive car for drag racing, what
kind of shock valving would you use?
A: There are
quite a few variables about the car that must be taken
into effect, primarily power and traction. The valving
required for a slick-tired, 500-horsepower Civic will be
different from a lightly-modified, street-tire Civic.
Generally, the theory is to limit and control weight
transfer at launch while maintaining a drivable car for
the high-speed end of the track.
The laws of
physics say that the harder you launch, the more weight
will transfer from the front to the back of the car and
unload the bite of the front tires. You can't get away
from weight transfer, but you want to try to control it
the best you can.
Ultimately, your 60-foot times
are the tool to quantify your launching ability. Having
an adjustable shock will allow you to tune your
suspension and compare your 60-foot times to pretty
easily dial in for the best results. By making very few
changes to the car and making consistent runs, shock
adjustments will show up in better or worse 60-foot
times.
As a rule of thumb, a front-driver will
want to try to keep the front tires loaded as much as
possible, so a relatively stiff front shock rebound
setting that will limit front-end lift would be good,
but since you can't stop weight transfer, you don't want
to be so stiff that you start to pick the tires up off
the pavement and remove bite.
On front
compression, you will want a relatively soft amount so
that it will readily accept from the rear any weight
that is initially transferred at launch. On the other
hand, you don't want it too soft so that you get wheel
hop (your tire sidewall stiffness will factor
here).
On the rear, a relatively soft rebound
setting will allow the release of weight that
transferred to the rear. Balance this with the need for
enough rebound to control the motion of the probably
stiff rear springs so the car doesn't pogo stick or
oscillate down the track.
Rear compression will
be pretty stiff to resist initial rear weight transfer,
but too stiff on a bumpy track will make the back end
want to dance around nervously at speed. Occasionally we
hear horror stories of front-drive racers removing rear
springs and shocks in lieu of solid bars to stop
transfer, but you just can't stop the laws of physics.
Instead, you then are requiring the tire sidewall to
become the suspension that it wasn't made to be. Better
to allow some motion and try to control it than to have
a 100-plus-mph solid skateboard.
Q: On a car with
adjustable shocks, how would you set them for a FWD
car?
A: Make a baseline run with the settings at
soft and look at your 60-foot times. Make consistent
passes (change nothing else on the car) while adjusting
the shocks in small increments. You should see your
60-foot times drop slowly until they even out and then
increase.
Once they increase, go back to the
settings that gave you the quickest 60-foot time.
Balance this with drivability on the high-speed end of
the track. No use in a great launch setting if it is
scary or makes you spin out at speed.
Q: Any
other advice for shocks in this situation?
A: The
more power a drag car makes, the more important it is to
assure that the power gets to the ground efficiently.
Energy wasted on wheel spin is energy not being used to
propel the car forward, so damping and shock valving
become increasingly important.
Every
engine/drivetrain layout has its own special needs. The
squatting characteristics of independent rear
suspensions are not an issue on solid-axle cars. Weight
transfer that benefits rear-drive cars hampers
front-drive cars. In each of these applications, shocks
companies that can customize, rebuild, or revalve
dampers to meet those needs will be better equipped to
improve the launch control and therefore the time slips
of the car.
Sources
Ankeny Racing
Enterprises 4790 Del Rio Street Simi Valley, CA
93063 (805) 527-1137
true, but theres
alot of good info in there that the majority on thsi
site overlooks when buying suspesnion. some buy things
just cause they heard of it, not cause tehy need it...
Re: Something you all can find useful in
your setu
Thanks for posting
all of that info (my eyes are a little tired now,)
maybee we can have some of it posted in the FAQ so you
don't have to write that novel again.
Re: Something you all can find useful in
your setu
not a prob LNDON
z24, been reading alot of suspension this semester.
heard the quote about
"you'll never see an
olympic runner with weak ankles" pertaining to build a
bas eto put the power to teh ground before anything else
and i've been reading up on things.
just another
addition, found on mantaparts site. alot of people on
this site have said larger front swaybar only will make
the car nuetral or give oversteer in he past 3-4
months... this should cover that...
What should
you do to improve suspension & handling:
The
GM FWD cars are inherently designed to keep going
straight if pushed to their limits, this is called
"understeer", which was built into the chassis to
provide more handling stability- not the best cornering.
A car going straight in a critical situation is better
than one spinning (oversteer) out of
control.
Springs & shocks- The modifications
we provide are aimed at giving the chassis better road
holding with improved shocks and springs for lower the
center of gravity and giving more control of the chassis
in all conditions. Our years of racing experience and
work with suspension engineers form GM and other
companies have led us to building a full line of shock
and strut upgrades for the GM small cars- more than any
other major manufacturer in the auto industry. Check
around, our struts have earned a good reputation in many
forms of sports and competition events.
Swaybars-
Also called anti-roll bars. The next thing you want to
do after lowering the car some is to decrease body roll
even more with swaybars- which also serve as a nice
chassis tuning tool since there are different sizes to
create levels of handling improvement to suit you
driving needs. FWD cars need MORE rear swaybar in any
application to reduce the built in understeer of the
chassis. The larger the rear bar the more neutral (and
beyond) you can tune the chassis. At some point a larger
front bar will balance the car and flatten the handling
even more.
Strut braces- These do not effect the
roll stiffness of the chassis per se, but actually
control chassis stiffness so that during hard cornering
the unibody stays put, and the moveable suspension
components can do their job consistently. They improve
steering and handling feel the same way with less
defection or movement of the related parts from their
designed locations, while the shock, springs and
swaybars, etc. are controlling the chassis- the same way
every time you
drive.
Re: Something you all can find useful in
your setu
very nice info,
thanks, but doesnt the second number in the tire size,
represent the percent of the first one ? like a
215/45R17 the tire width is 215 millimeters, the 45 is
(45% of the width which is 215) just curious, cus you
see a cav with 225/35/18 and a a viper with like
305/35/18 or 19 and the sidewall is alot bigger on the
viper, cus 35 % of 305 is more then 35 % of 225, just
curious, if im wrong let me know, thanks
Re: Something you all can find useful in
your setu
actually the
second numver referes to the height of the
sidewall...
check it out:
The
first number is the width of the tire in millimeters,
measured from sidewall to sidewall. To convert to
inches, divide by 25.4 In the example above, the width
is 185mm or 7.28".
The second number is the
aspect ratio. This is a ratio of sidewall height to
width. In the example above, the tire is 7.28" wide,
multiply that by the aspect ratio to find the height of
one sidewall. In this case, 185x0.60=111mm or
7.28"x0.60=4.36".
The last number is the diameter
of the wheel in inches.
To figure the outside
diameter of a tire, take the sidewall height and
multiply by 2,(remember that the diameter is made up of
2 sidewalls, the one above the wheel, and the one below
the wheel) and add the diameter of the wheel to get your
answer.
Example...185/60R14 85H or
185/60HR14
185mm x .60=111mm x 2=222mm +
355.6mm(14")= 577.6mm or 22.74"
Re: Something you all can find useful in
your setu
****lndonz24, i
didn;t have your email to send the word file, bt i sent
it through the site... let me know if you get
it...*****
Brake Pad
Choice
Increasing your braking performance is one
of the easiest-and cheapest-ways to lower lap times. By
shortening your braking distances, you can stay on the
power longer and drive deeper into the corners. This may
sound academic, but too many racers take brakes for
granted and thus neglect one of the most important
aspects of their car's performance. On the track, as
well as on the street, good brakes can also be the
difference between life and death.
One of the
easiest ways to increase your braking potential is to
select the right compounds for your brake pads and
shoes. Spending lots of time and money retrofitting
trick, aftermarket big brakes could be a waste if you
haven't first maximized your current brake
setup.
Proper pad and shoe selection can make the
difference between being a back marker and being a
contender. Carbotech Engineering's Larry Narcus-a
chemist with 30 years experience in plastics who has
since decided to devote his energies to manufacturing
better brake pads and shoes-tells of a customer with an
Improved Touring Corvair came to him looking for some
shoes. Now, if you're familiar with Corvairs, then you
know that they have big drum brakes at all four corners.
Not exactly high-tech, but according to Larry, they can
be made to stop well with the proper shoe selection.
Next time out, with the proper shoes in place, the
Corvair driver dropped six seconds off his lap times.
Think about that: six seconds. How much would you pay to
drop that much from your lap times? Not All Compounds
are Created Equal
What's the secret to choosing
the right pad or shoe? Obtaining a basic understanding
of your needs and then matching them to the proper
compounds. It's also useful to listen to the experts
(hopefully, the people selling the stuff).
Brake
pads and shoes, like a lot of things in this world, are
available in a large number of flavors. Some are good,
and others are so-so. Understanding this will make life
easier. Let's take a look at what kinds of compounds are
available:
· Organic: These are the $6.99 pads
that you can get at the local parts shop; essentially,
you get what you pay for. Organic pads are made up of
compressed wood and/or paper, and perhaps some low-grade
metal has been thrown in. Their friction coefficient
(how well they grip against the rotor or drum surface)
is very low, and they can't handle the high temperatures
associated with any sort of performance driving.
Basically, these pads not appropriate for competition
use.
· Semi-metallic: These are definitely a step
in the right direction. Expect to find much more metal
in the mix (probably iron, but maybe brass or bronze)
along with a better binder (what holds the pad
together). The friction coefficient is higher (meaning
the pads will provide more bite against the rotor) and
they will wear better. Semi-metallic pads and shoes are
the basic $30/pair-type found down the street. Usually a
better choice over organic compounds, but you could do
better.
Carbon-based metallic: This is the good
stuff that we'll be talking about today. The price goes
up a bit, but performance rises many times over. Carbon
and various metals (iron, nickel, brass and bronze) are
thrown into the mix, and a better high-temperature epoxy
binder holds everything together. The friction
coefficient is much higher than semi-metallic pads, and
in general they are also less dusty. Carbon-based
metallic pads are offered by several companies in many
different compound mixes. Hawk, Performance Friction,
Porterfield, Cool Carbon and Wilwood (Polymatrix) all
offer quality carbon-based metallic pads. Besides
selling brake pads, Carbotech and TS Imported can also
reline the backing plates from drum brakes with these
modern materials.
· Carbon-carbon: Odds are you
don't have these brakes (carbon-fiber rotors with
carbon-fiber pads), unless you run in FIA races in
Europe.
Choosing a Compound
Even
carbon-based metallic pads are available in different
compounds; choosing the right one may require some
research and soul-searching. Basically, you need to
match the right pad to your application. If you're
worried that no one has pads or shoes for your oddball
application, rest assured that some suppliers can do
custom installations or reline your existing backing
plates. But how do you know which pad is right for
you? Well, since no pad can do it all, you need to look
at several different areas of concern when shopping for
brake pads and shoes. By discussing these concerns with
the different suppliers, you should be able to match
your needs to the right product.
· Your first
concern should be stopping power. This is measured by a
friction coefficient, and the higher the coefficient,
the more stopping power available from that compound.
However, compounds with very high friction coefficients
tend to be hard on rotors and drums, which may not be
desirable in some situations (like on the street or in
an endurance race). Like most things in life (brake pads
included), it's a trade-off where you must look at the
whole picture and decide which concerns are most
important for you and your application.
·
Modulation, the lack of the tendency for the brakes to
lock up, is also a high concern for most of us.
Modulation helps control the car, as locking up the
brakes can put you in a spin. Again, different racers
need different degrees of modulation. An autocrosser, to
whom every hundredth of a second is valuable, simply
cannot afford any lockup. Therefore, lots of modulation
is important to him. An endurance racer, on the other
hand, can deal with less modulation if it means getting
longer pad life.
· Fade resistance is another big
factor. Every compound has a temperature range in which
it likes to operate; matching the compound to your brake
temperature range is crucial. Most racing pads have a
600 to 800 degree window for their operating
temperature, while brake temperatures generated by
street driving tend to be much lower. So there is no way
a great road race pad designed to work under high
temperatures is going to stop well on the street.
Nevertheless, many people seem to labor under a major
misconception as they buy "racing" brake pads for their
street cars and, when these pads fail to meet their
expectations, they feel cheated. Be honest with yourself
and buy wisely. Likewise, a heavier car is going to
generate more heat than a lighter car. By working with
your vendor, you should be able to match your driving
conditions to the proper compound. Tell them what
conditions you race under, what tracks you visit and how
hard you are on the brakes.
· Rotor and drum
friendliness can also be a factor to some drivers,
especially those with older cars. Some compounds, while
they'll stop you on a dime, can be very hard on rotor
and drum surfaces. If you race a car for which these
replacement parts are hard to find, like a vintage
Bugatti for example, then having friendly pads and shoes
may be a prime concern-perhaps even more important than
absolute stopping power. Likewise, a set of pads that
will chew up a set of rotors every three hours will be
of little use to a racer about to run a four-hour
enduro.
· For a lot of us, economics also need to
be addressed. However, don't simply look at the final
price when shopping for new pads and shoes. If a pair of
brake pads costs twice as much as the competition but
lasts three times as long, which is the better
deal?
· While not a huge concern for everybody,
brake dust and squeal can be a factor for some people.
If neglected, dust can attack the finish on a set of
wheels, quickly turning a prized set of rims into an
eyesore. At the extreme end, hot flakes from the brake
pads can land on the fenders of a car, singing the
paint. Now, a road racer may be willing to pay that
price, whereas a street driver may not. For a lot of
people who only drive on the street, squealing brakes
can be a major inconvenience. If you don't like being
tortured by a set of wailing brake pads, move this
consideration to near the top of your list.
· The
rate of wear is also something to think about, although
it is related to many of the factors we already
discussed. But to bring back our endurance driver, it
may be the most important factor when selecting new
shoes and pads. Again, be sure to discuss this factor
with the guys selling the goods.
Speaking of
wear, some companies offer slightly thicker pads
designed for endurance racing. As a side benefit, these
thicker pads seem to handle heat better and provide
better braking characteristics. (The more pad material,
the bigger the heat sink). While extra-thick pads may
seem like the answer to everyone's problems, there is a
limit-make the pads too thick, and you'll need thinner
rotors, which is not a good move. Matching the Pad to
Your Application
The biggest part of buying brake
pads is matching the compound to your application. So,
let's take a look at some common applications and what
kind of braking compound characteristics they
require.
· Though they may seem different at
first, autocrossers can require the same compounds as
high-performance street drivers. Both need effective
cold stopping power and lots of modulation. In
autocross, there is no time to bring the brakes up to
the temperatures required by many "racing" brake pads.
You need full stopping power right off the line, and you
need it right away. Likewise, when out on the street,
you also have no time to wait for brakes to heat up, and
here the stakes are a lot higher. On the street, your
brakes have a lot of time to cool off between stops, so
it is important to pick a pad that will be happy to work
while cool. For both applications, look for compounds
designed to work in the 100- to 800-degree
range.
Modulation is also important, both when
autocrossing and on the street. It's the kiss of death
for an autocrosser to lock up a brake. A skid means lost
time, which means the run is junk. With only three or
four runs at an event, that can be the end of any
chances of a trophy. On a road course, a racer can
usually overcome or bounce back from a skid on the same
lap; autocrossers, by the nature of their sport, don't
have that luxury. Cost and a lack of audible squeal
can also be factors, depending upon the individual. Some
of us are also willing to live with more dust than
others.
· Track events and drivers schools are
gaining popularity; these drivers also need to select
the right compounds for their needs. Generally, they
will be looking for good modulation and lots of stopping
power. The main difference between them and the
autocrosser is the temperature range of their brakes.
Generally, and depending upon the car, driver and track,
they'll need to select a compound that works in the 300-
to 1100-degree range.
These pads and shoes
require some heat to work properly, so you should
strongly consider swapping to these "track pads" before
heading out on course-just as you mount sticky tires
before an event. · Road racers, whether they be sedan
or formula car drivers, also have to look at more at
fade resistance. Stopping power and modulation is still
very important, but fade resistance throws a new factor
into the equation. This will require a pad that can work
in the 400- to 1400-degree range, depending on track,
car type, length of event, level of brake cooling and
driving style.
As road racing conditions can
change from event to event, you may want to consider
using different pads for varying conditions. Remember
that a track like Sebring is a lot harder on brakes than
Roebling Road. Weather conditions can also cause a
change in braking compound requirements. In the rain,
you may need more modulation than all-out stopping
power. Racers are eager to change tires when faced with
rain, but why not brake pads? In some situations, like
at last year's rainy ARRC, rain and its effect on
stopping power is a deciding factor for many
drivers. Economics and rotor/drum friendliness can
also be factors for road racers, especially those
running endurance events or driving older cars for which
replacement brake parts are getting harder to find. As
we discussed before, rotor and drum friendliness may be
top priority for a vintage car racer.
So, which
brake pad is best for you? Unfortunately, there is no
way we can tell you exactly which pad or shoe will work
best for your application. Hopefully we have educated
you enough so that you and your retailer of choice can
intelligently discuss your needs and match you up with
the proper compound. Doing so may take some testing and
time, but in the end you'll have the stopping power you
need. Brake Fluid
While you're focusing on
brake pads, don't forget to check out your brake fluid.
If you can't remember the last time you changed your
brake fluid, do so now. Brake fluid absorbs moisture
over time, which causes a large number of problems,
including spongy brake feel, rusting components,
etc.-none of which you really want to deal with.
Speaking of brake fluid, remember to bleed it often at
an event, especially if you're racing in a humid
climate. Your brake fluid is expected to work under some
incredibly hot situations. In many cases, this is also a
weak spot in the system. When buying fluid, remember
that the higher the rating, the better the stuff. DOT 4
fluid is better than DOT 3, and DOT 5 is better than DOT
4. However, beware of silicone-based DOT 5 fluid-it can
give you a mushy pedal. Go with glycol-based DOT
5.1.
Brake Lines
When you stomp on your
brake pedal, the fluid not only pushes through the brake
lines, it also pushes against the brake lines, causing
inefficiency in the system. How can you combat this
loss? Replace the stock rubber brake hoses with braided
stainless-steel lines. The swap is fairly easy and
inexpensive. Expect a firmer pedal when done. Check your
rulebook before making this mod; also, not all stainless
lines are DOT-legal.
Brake Ducts
Brakes
work on the simple principle of converting kinetic
energy into heat energy; helping your brakes get rid of
that heat will allow them to function more efficiently.
Hence, a little duct work may be in order. Scoops and
duct materials are available from numerous race shops.
Likewise, running wheels that have a lot of space
between the spokes will also help disperse
heat.
Master Cylinder
Is your master
cylinder junk? Then either replace or rebuild it right
away. As the heart of the braking system, a master
cylinder's health is vital to proper braking. If it's
time to replace your master cylinder, remember that
bigger is not better; moving to a master cylinder with a
larger cylinder diameter will result in lower line
pressure, causing less pressure between the pad and the
braking surface. This is bad.
Bias
Knobs
Have you severely lowered your car? Doing
so can mess with the front-to-rear brake bias, which now
needs to be changed. A brake bias knob, located inside
the cockpit, allows the driver to adjust the brake bias
as needed.
Pedal Covers
It may seem
obvious, but having slippery brake pedal covers can
hamper braking. Ever step on the brakes and have your
foot slip off the pedal? Whether you install some fresh,
new, original-equipment rubber pedal covers or trick,
drilled-out pieces, you'll be in better
shape.
Practical Test
All of this talk of
brake pads is great, but we needed a little practical
exercise to back it up. We wanted to measure how much a
swap in brake pads alone would change things in the real
world.
For the test vehicle, we grabbed our
editor's 1988 Honda CRX Si. Several factors made his CRX
a prime candidate: First, with almost 170,000 miles on
the clock, this car's brakes were nothing to write home
about. The system had been well maintained during that
time, but the brakes were average, at best. The fluid
was fresh, but the system lacked any real bite. We
also wanted to see how well a disc/drum system could
work with the proper compounds. A lot of people consider
drums yesterday's news, but we wanted to see if a set of
modern compounds would make them happy. Finally,
big-brake swaps on Hondas are all the rage. Everyone and
their brother is touting cross-drilled, slotted and
over-sized rotors for the front and rear of Hondas. We
wondered if could we get killer performance for a
fraction of the cost and without the hassles of
re-engineering our brake system.
Baseline
Tests
Before performing any baseline tests, we
refilled the brake system with Castrol LMA brake fluid,
bled the brakes and checked our tire pressures. Except
for the Personal steering wheel and AutoThority
short-shift kit, the rest of the car was bone
stock.
We grabbed our Vericom VC2000PC on-board
data acquisition system, put J.G. (our resident hot-shoe
driver) in the driver's seat, and set out for our
top-secret test site.
Then we did some baseline
tests. Our first stop from 60 mph took only 148 feet
while generating .875g of force. The stop took 3.62
seconds, and some right-rear lockup was
observed.
By our second stop, the pads were
already showing they were giving up the fight-it took an
additional 10 feet to stop from 60 mph. Our g force
readings had fallen to .840 g, and the stop took 3.83
seconds. Things didn't get any better after that. Our
CRX took 161 feet to come to a halt by the fourth run.
Fade was running rampant, and it was already time to
allow the brakes to cool off. We ran some more stops
that day, and our g force readings hovered in the .84 to
.88 range. The average was .858g over the eight stops we
measured. Before heading home, we had to drive around a
bit so the brakes could cool.
Looking to
Improve
With our baseline figures in hand, we
started our search for new pads and shoes. This is a
street car, remember, so cold stopping power is very
important. We also plan on autocrossing the car, so fade
and modulation were also high on our list.
Larry
Narcus at Carbotech listened to our requirements and
matched us up with the goods. Up front we would try his
new "Mean Green" Kelated-metallic pads. These are
designed to work in the 100- to 750-degree environment,
perfect for the street and autocross use. He also
promised no fade and excellent modulation. For the
rears, we would try his Silver Streak shoes. These offer
a slightly lower friction coefficient than the Mean
Greens and would compliment the Kelated-metallic front
pads, he said. Randy Duval at AllSpeed helped install
the new pads and shoes, which were no harder to install
than your garden variety OE pieces. We found our
original-equipment pieces to be rather worn, probably
not entirely unlike most street cars out there. Our
rotors were looking a bit thin, but we decided to keep
them on and see what the pads alone would do. With
the Carbotech pieces installed, we followed Larry's
instructions and properly bedded in the pads. Then it
was time for more testing. J.G.'s first run on the
Carbotechs registered an astonishing .929 g. However,
the stop took 162 feet. This was probably due to the
fact that the pads were still unfamiliar with the
irregular surface of the rotors. Also, our CRX had
average street tires on it, but like we said, we wanted
to simulate a real-world test.
The next stop saw
the distance plummet to 144 feet at .896g. The stop took
3.40 seconds and J.G. reported that modulation was
excellent. We ran seven more stops that session; by
the end we had the stopping distances down to 141 feet.
Even towards the end of the test, the brakes were still
stopping well, showing g force readings as high as .995g
after half a dozen repeated stops from 60 mph. We
averaged .923g over the nine stops we recorded with the
Carbotech shoes and pads. Our stops took as little as
3.18 seconds and the stopping distances were now as
short as 140 feet.
At no time during this test
did we observe fade or any modulation problems. Unlike
the stock pieces, we never had to allow the brakes to
cool off once we installed the new shoes and
pads.
These tests were all conducted literally
minutes after the Carbotech shoes and pads were
installed, so naturally the braking performance should
only get better as the pads conform to the rotor
surfaces. We have gone ahead and ordered some new
rotors; we can't wait to see how the pads work against a
fresh surface (we'll have the pads resurfaced before
installing them). As for tires, we'll test the car again
once some fresh rubber arrives. Remember an important
fact: the brakes stop the wheel; the tires stop the car.
Your brakes are only as good as your weakest link in the
system, and right now our tires can't keep up with our
brakes. And yes, all of this data will appear in a
future issue.
This simple brake pad and shoe
change has given us fantastic brakes for a fraction of
the cost of a over-sized, drilled rotor conversion. It
may not look sexy, but it certainly gets the job
done.
Any down side to these pads? Not really,
although we have gotten some squeal under low line
pressure situations (like when slowly rolling to a
stop). There is also some dust, but that's why wheel
cleaners were invented. Still, for day-to-day driving,
we have to say that these brakes are
perfect.
Trusims:
In the world of braking,
there some facts that are undeniable.
· A brake
pad or shoe that isn't wearing isn't working. Remember,
the things have to wear to work.
· You're
going to get what you pay for. (Where isn't this
true?)
· There's a brake compound out there for
everybody; you just have to do some looking to find
it.
· No one really knows what causes brake
squeal. All brakes produce squeal, but our ears cannot
always hear it.
· The rear brakes are there for a
reason. Just because the fronts do most of the work,
don't neglect the rear brakes.
· Brake pads and
shoes are only part of the story; make sure your entire
braking system is up to snuff.
Some brake pad
suggestions based on
end-use:
High-performance
Street/Autocross
Hawk HP Plus, Black PFC
Street Pads, Z-Rated, 80 Compound Porterfield R4,
R4S Carbotech Kelated-Metallic
The offset of a wheel is the distance from
its hub mounting surface to the centerline of the wheel.
The offset can be one of three types.
Zero
Offset The hub mounting surface is even with the
centerline of the wheel.
Positive The hub
mounting surface is toward the front or wheel side of
the wheel. Positive offset wheels are generally found on
front wheel drive cars and newer rear drive
cars.
Negative The hub mounting surface is
toward the back or brake side of the wheels centerline.
"Deep dish" wheels are typically a negative
offset.
If the offset of the wheel is not correct
for the car, the handling can be adversely affected.
When the width of the wheel changes, the offset also
changes numerically. If the offset were to stay the same
while you added width, the additional width would be
split evenly between the inside and outside. For most
cars, this won't work correctly. We have test fitted
thousands of different vehicles for proper fitment. Our
extensive database allows our sales staff to offer you
the perfect fit for your vehicle.
Re: Something you all can find useful in
your setu
yup john, no
copyrights on any of it. some of this i pulled out a
book i am reading on suspension, so typing it was a
b*#$%. but everything else is just
exceprts
Re: Something you all can find useful in
your setu
getting ready to
rebuild the suspension on the '93. needed to chew on
some that stuff. My head hurts now, but thanx for the
work putting it all up,
eh.
Oooh...
Doughnuts.
Re: Something you all can find useful in
your setu
articfire, not
sure as of yet, looking for a spring dyno around here.
EIP tuning is open here in Md tomorow. i dont mind
shelling the cash to find out... thing is the stocks are
agreeably softer than any coils you can install right?
so we knw they may be in the 3250 range. but heres the
other factor to no overlook. the stock springs are
progressive right? well the bottom coils will obviously
be thicker and a higher spring rate with the smaller
coils being a lighter spring rate. thats the tricky
part.
i'll get it figured out soon though.
still reading about seeing if there is a way for a
progressive spring rate to be accurately
measured.
Re: Something you all can find useful in
your setu
also alot of you are asing about
26mm bars, i highly suggest you read mantaparts page on
sway bars which states they are not to be used without
another bar to somewhat offset it. sure it may look cool
to have one tire up in the air, but that hurts handling.
26mm bars are too large to be used alone without a bar
on the other end to offset it to some degree. and by
bars i am referring to
swaybars.
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