Blackwater 9/8/2010To put it simply, a camber kit adjusts the inward or outward tilt of the wheel caused by.
1. Finding excessive tire wear on the inside edge of your tires compared to the outer edge
2. Taking your vehicle in for an alignment and asking the technician if you have excessive negative camber (and for a printout of the results). This is the only way to know exactly how excessive your camber is but definitely not necessary.
3. You have lowered your vehicle so you already know your alignment (camber) will be off and purchase a camber kit ahead of time.