ROCKERS
As you can see in this photo, the Rockers are pretty basic and simple.
Start with 2 pieces of the 1 1/2" x1/2" flat stock, long enough to extend about 2 inches behind your wheel. Don't weld the bail piece on yet. This is the part where we find out what the width of your Trees will need to be.
Using the proper spacers and washers if needed, center the wheel between your 2 rockers. Bolt it all together and tighten the bolt to proper tightness. Now we can measure the space between the rockers from behind the wheel. Write that measurement down. If you want you can go ahead and cut a piece to weld to the rockers across the back so it will all be one piece. The next step will help you finish the measurement for your trees.