Rack stud spacers: Spacers at the ball studs on the rack change the Ackermann angle which controls how much the car’s toe angle changes as the wheels are turned either direction. Most cars are set up so that the toe-in angle decreases (toe-out increases) as the wheels are turned in either direction.
Fewer rack stud spacers / lower Ackermann angle
More rack stud spacers / higher Ackermann angle
Steering arm stud spacers: Spacers at the steering arm (aka “spindle” or “steering block”) control the car’s “bumpsteer.” Bumpsteer is the change in a car’s toe angle as the suspension compresses. If you change camber link locations, toe-in, or kick-up, you may need to re-adjust bumpsteer to keep the handling characteristics consistent.
Fewer steering arm spacers / less bumpsteer
More steering arm spacers / more bumpsteer