2nd gen is350 tire size question
 

I need new tires on my 06 RWD is350 on aftermarket 18" wheels. The tires are the standard tire sizes for the stock 18" package (225-4018 fronts, 255-4018 rear) and want to see if it wouldn't hurt the car to get tires all the same size. Which size is recommended? Have any of you done this?

What's the aftermarket 18 spec?

Wish I knew. How would I find out?

The only resonable way to do this is to put 245/40s front & rear. I wanted to do this but since the rear tire will be shorter it will make the odometer register miles faster than actual & that will hurt @ resale time.

FIRST, you'll need to get the specs on those wheels. Pull them off and make note of the numbers (ie "18x8.5" and "ET 35") on the inner part of the wheel.

Once we know the offset and size, we can tell you what is the largest size tire you'll setup can possibly manage.

Are you on stock suspension...aka, NOT lowered?