Hello.

I've tried to do sufficient due diligence by researching this issue in this and other forums, but I haven't found the answers to these particular questions, and I'm still stuck.

I have a 2007 G35 Sedan, which originally had the following stock 18" tires:
Front: 225/50/18 (26.9" diameter)
Rear: 245/45/18 (26.7" diameter)

As many others discovered, there are not many all-weather wheels available in these unique sizes. So, I opted for slightly different tire sizes.

My new tire sizes are:
Front: 235/50/18 (27.2" diameter)
Rear: 255/45/18 (27.0" diameter).

Both the old set and the new set have a difference of 0.2" diameter between the front and the back. Additionally, the size differences between the old set and new set are less than the 3% I've read about in several places.

Soon after the tires were replaced, I noticed that the dreaded VDC, SLIP, and sometimes the BRAKE light would come on. Now, well over a year after the tires have been replaced, the VDC and SLIP lights seem to be on permanently.

I understand that differences in the front-to-rear sizes can wreak havoc with VDC, or if the new tires are significantly different in diameter (>3%). However, neither seems to be the case with my new tire combination.

A few questions:

1. Can the VDC be "reset"? I've heard that the VDC is somewhat adaptive to account for tire degradation, was curious if there was a way to try to reset it and see if this would fix the problem.

2. Do you think that the new tire size combinations could be the culprit even though they fit within the specifications I"ve seen online?

3. Any other ideas that I should check to try to fix the problem? Is my only recourse to purchase 4 new stock-size tires?

Thanks for your help.

 

Problem is not in wheel diameter, problem is in difference in revolutions per mile.
Your old set had 772/778 revolutions per mile or 0.8% difference
New set 771/798. That is 3.5% difference. If 3% rule is correct, you are in trouble.

Why don't you hook up with local fellow G35 owner and borrow factory set for test drive? It will rule out that something esle is wrong with VDC.

Edit: I do not know your tire brand-check specs for you particular tires, they do differ from tire maker to tire maker. WTF? How 27.2" bridgestone can differ in rpm from 27.2" michelin!? But that is a different topic....

 

My brake light, VDC, and Slip lights all came on once when my rear pads were low, with only 1/4" of material left. I haven't seen it on for three years after I replaced the rear pads.