The effect of bump steer is for the wheels to toe-in or toe-out when the suspension moves up or down. Bump steer is undesirable because the suspension is steering the car instead of the driver. To fix bump steer especially when lowering a car you need to alter the height of the outer tie-rod relative to the steering rack with adjustable tie-rod ends also known as a bump steer kit. BBK Performance Mustang Bump Steer Kits are available to fit 1979-93 1994-04 and 2005-14 Ford Mustangs. These BBK Bump steer Kits will correct the front geometry of the Mustang suspension after you have lowered the it with a Mustang lowering spring kit.
This bump steer kit will offer improved steering and better handling. These kits can also be used to replace stock factory tie rod ends that wear out instead of replacing the ball joints.