Originally Posted by Crashby

It is very important to have your rear track, as well as your front track, equally spaced from the center line of the car. The axle shims/spacers allow you to do this. They are available from several sources and come in different thicknesses. Most 1/12 cars work their best when the rear track is also at the legal maximum. These spacers help to get to that effect.

I use the Niftech alignment tool. (See the link below) This tool quickly determines if your track is equally spaced. A must have tool for pan car racing.

http://www.niftech.com/catalog/index...ode=3000series