Reply to "Steering rack shims"

According to experts like Carroll Smith, author of the "XXX To Win" series of books, all of the bump-steer cannot be removed from any given steering system because of geometry conflicts. All you can do is minimize the effect by smaller and smaller repetitive changes. You first find what you've got by removing the coil-over on one wheel, setting up a plate with two dial indicators -one touching the wheel rim on the outside face at front and one at the back, and begin raising the wheel up 1/8" inch at a time and reading the variation in wheel position, graphing the full travel up/down vs that wheel's position. Then you change the shim thickness and measure it again, seeing if the bump-steer toe change, in the area of travel used most by your car, is better with this shim size. You keep doing this until you get tired or the thing is about as good as it can get in the wheel-travel area you use in your driving. Then you realign the wheels (toe-in changes with rack position height), check one more time to verify this adjustment didn't detract from your results, and call it done. NO ONE (including me) does this outside of racecar crews on cars that earn money racing. 5/16" is close enough, I believe.