Looking for some new tires for my 03 coupe. Would changing from OEM 225/45/18, 245/45/18 to 225/45/18 and 245/40/18 pose a problem? Just changing the rear profile.

 

It wouldnt cause a problem, but why would you want to go with a lower profile in the rear?
-GP-

 

The tires I'm looking at do not come in 45, Kuhmo SPT's.

 

I would think 245/40s in the rear *would* cause problems. Specifically with the VDC. Dropping the profile like that is going to reduce the overall diameter by 3.75%, making the rears spin faster by that amount. I don't know how sensitive the VDC is, but if its differential threshold is under 3% you may have to keep the VDC off with that setup.

I'm shopping around for tires on the OEM 18" rims as well, and one thing I want to maintain is the stagger between front and rear to avoid having the VDC go nuts.

I want wider rubber front and rear, but I'm having trouble finding the tire models I want in the sizes that stay as close as possible to the 2.656% rotational speed differential between front and rear.

The best options I've come up with are 235/45ff 255/45rr or 245/40ff 245/45rr but sizes are hard to find in the first combo, and I'm concerned about the VDC in the second.

I have been unable to find details on the sensitivity threshold of the VDC. I would think selecting a size package that spins the fronts slower than stock would be ok, but who knows?