Feb 11, 2013
Port Perry/Peterborough
1999 C5
I currently have the Z06 style rims on my stock C5.
I was wondering about tire fitment as I need to replace my weather cracked Proxes.

The current tires are 245/40ZR18 and 285/40ZR18

I have located a very reasonably priced set of tires that are 255/45ZR18 and 285/40ZR18.

Will this swap work? Will I experience problems? Thanks in advance guys!'

Those tires will fit just fine....physically. However, the problem is that they are approximately the same diameter with the fronts being a little larger. This will cause issues with the AH/TC system. You want the rear tires to be at least .5 inches larger in diameter with a maximum of 1.5" larger for the AH/TC to work properly.
All the electronique wont be affectyed by the width (about 1/2 inch of difference). My concern is about the diffence in diameter that is over 5%. Normaly you try to stay under 3%, with 5.1%, I am not sure of how abs or traction control may react or react to fast. Go to this web site and enter both sizes, you will see the difference. You can also enter the 2 oem sizes to get the oem difference in diameter and rotation/miles from front to rear then enter the new sizes.

On my car, I would not switch tire size unless the difference in diameter isint bigger than the difference between a new and a worn out tire.

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