: Rims Question-AWD 1SG

05-29-09, 01:39 AM
I have an 05 STS4 V8 1SG. The Premium Luxury Performance package includes 18' wheels with 255/45-18 on the back and 235/50-18 on the front. This struck me as funny as the front and rear tires are .8% different in overall diameter on an AWD car....but then I looked at a co-workers 2006 AWD with the factory 17's and noted that her car has matching tires (235/55-17, I think) at all four corners. Surely the transfer cases on our cars are the same, right? If so then has Cadillac built in the forgiveness of a small variance in tire sizes front/rear? I once had a tire guy tell me that I shouldn't buy just two tires for my AWD Honda Pilot if there was more than 2/32" difference in tread depth. I would like to put rims on mine but am scared to death of screwing something major up by either not staggering the new wheels/tires at all or not enough.....not sure what to do here. Any input would be appreciated.

05-29-09, 04:16 PM
It has an "open" differential between the front and back just as it does side to side so small variations are no problem. Large variations can cause a diff to burn out over time. Also, remember these cars can tolerate the compact spares with no problem (although not for extended periods)

05-29-09, 04:28 PM
There are adherents to both sides of this issue. 'It doesn't matter' or 'You'll ruin your car!'

I personally do not believe GM changed anything when equipping my STS4 with the same staggered setup. The DPO & dealer rotated the tires three times before I got the car, so the 255/45-18's spent over 25,000 miles on the front! I'm over 45k and no trouble yet!

That said, I'm probably going with 255/45-18's all around when I replace them. I didn't have any rubbing issues while they were reversed!