I went through this exercise several times, becoming more and more frustrated each time I couldn't get the readings (camber) to repeat. And I while I might agree in principal with what Andy had to say, his term "minimal amount" leaves a lot to be desired. Let's quantify... I've found that 1/4 inch difference in floor elevation across a diagonal (e.g. LF to RR) will screw up camber readings beyond belief, particularly with an IRS vehicle. And as for corner weighting, even at half that variation, you might as well not bother. And there are many, many garage floors that will simply not meet that criteria.

I finally bought a good builder&#39;s laser level and found a basically level area of the shop, drew 4 squares in that area for the 4 tire patches, then leveled to perfection (< 1/32") with thin (cheap) 12" x 12" floor tiles. You&#39;ll know you have it right when you can corner weigh the car, then put it back on the same spots but headed the other direction, and come up with essentially the same corner weights.

As an aside, I once found the RR tire to be 2 or 3 psi lower than the other 3 tires in the middle of a corner weighing session. I aired it up and watched with amazement as the corner weights changed drastically. Be sure you&#39;re at target HOT tire pressures before you do any of the above.