Different Size Tires

Originally Posted by Masa

Ding ding ding! Winner.

The problem is now your rear tires are 1 inch diameter less than the fronts because of the 40 series sidewall. You need 45 series sidewall with a 245 width.

Right your your front 225/50/18 have an overall diameter of 26.8 inches and the rear 245/40/18 have an overall diameter for 25.7 inches. This is a 4% variance which will throw your abs/vdc out of sync causing instability issues.

You want to stay within 1% variance when running staggered set ups.