Adjustable rear-axle camber adjustment control arm kit for Mazda RX7 — TA Technix

Lowering a car automatically increases negative camber. A little is good for grip; too much, and the tire wears through its inner sidewall within a few thousand miles.

These parts bring camber back within the desired range, or allow you to deliberately add negative camber for track use. Beyond 40 mm of lowering, they are no longer a luxury.