I ran C5 rims on my 1998 Z28 and never had an ABS problem. The brakes were solid and I could bring them to modulate if I braked hard enough, but I could also brake very hard w/out having them cycle.
I think as long as the wheel rpms are close you should be fine. Tire height should be roughly the same, but I don't think have to be exact. I think where people run into problems is trying to run very low profiles on the front as well. 245/45/17's should be run on the front I believe if I can remember right. the rears I had were either 285/35/18's or something close to that.
GM coulnd't make it that exact anyway or else they'd have tons of service people complaining to high hell. Two different brand tires will have sometime sidewall height differences of 3/10's of an inch difference and if you put on new rear tires and kept your old different brand tires up front that could theorhetically trip your abs up if what you say is correct. I don't buy it. I thik the only reason the abs sends to the pcm is so that the low traction light on the dashboard displays and nothing else.

 

i only read through a page of the reply's. I have 17's on the front and 18's on the back and no ABS problems with my stock rear. And no abs problems with my home built abs setup on the new 8.8

 

Josh: You did read the post where tire diameter was mentioned right? The pcm....or abs for that matter...doesn't care what size rim you have. You could have a 20 inch rim in back and a 15 up from and it wouldn't care.....as long as the circumference of the tires were the same (the 15 inch would just have alot more sidewall to make up for the rim height).

Joe