Question: Kumho Ecsta XS rear sizing question

[napacruzerC5]

Interested in the Kumho Ecsta XS 180 rating for autocross/street use to be mounted on stock OEM '01 thins spokes. Fronts match the stock 245/45/17 while the closest size for the rears are 275/35/18 (stock rears are 275/40/18). Front diameter 25.7 while the 275/35/18 are 25.6. Some say having a shorter diameter on the rears will throw off the traction control. Opinions please. BTW Tire Rack has them at $142/$236 + SH.

 

[Mr. Lucky]

That smaller OD won't work well if you use traction control, although it will effectively give you a numerically higher rear end ratio (which will be good for accelleration). I think a better choice would be to investigate if they have stock C6 rear sizing, 285/40-18.

 

[Dave]

You're splitting hairs.
The difference between the two sizes results in 3.03 more revolutions in one mile using the smaller tire. The difference in circumference between the two tires is .31". That means that for every mile you drive on the larger tire, you lose .939 Inches traveled on the smaller tire.
Dave