Quick Facts

• Bumps steer is affected by Caster.  Every caster change increases or decreases raises and lowers the tie rod relative to the ball joint which can adversely affect bump steers.  Once caster is set, bump steer should be set for optimum braking and corner entry. 
• Proper bumpsteer provides stability to drag cars as they rise and fall during launch, during shifts, and at the far end at speed as the chassis settles down
• Necessary when ever you lower your car or alter caster settings.
• Allows you to adjust the bumpsteer

Bump steer is the racer's name for toe-change during suspension travel. You may not know it, but if you have lowered your car, you have a bump steer problem. Offset rack bushings may help, but adjusting bump steer is like adjusting ignition timing, it must be tuned for each car. The Griggs Racing bump steer kit makes it possible for you to tune the bump-steer out of any Mustang by positioning the steering linkage so that it is parallel to the control arm.

For more information please read the following:
"Been There, Done It All" October 2004, 5.0 Mustang and Super Fords (12.4 MB pdf )
The GR40 Suspension System
"Extreme Winner" May 2005, 5.0 Mustang and Super Fords (2.47 MB pdf)