My JK has the 'cheap' 16" steel wheels (225-75-16 tire).
I have an opportunity to buy the 17" aluminum stock wheels from another JK owner at a good price, with the stock 255-75-17 tires.

If I punch these sizes into a tire size calculator, I get 8.65% difference in diameter - 29.28" vs 32.05".

With both of these sizes being "stock" for the JK, does the dealer make a change to the computer to compensate?

Would I notice a difference in the overall gearing because of the difference?

Thanks

 

The dealer could reprogram your speedometer. It will be of 9% if you don't. But you won't notice much of anything power wise

 

I just did exactly the same thing, had the 225's and bought rubi take off's 255/75/17, the speedo was 5mph off and it felt a little sluggish. I had dealer reprogram the new tire size and speedo and shift points went back to normal. I have a 2dr with 3.73 gears and the power is fine to me. Even gas mileage stayed the same! dealer will charge to recalibrate computer, so you could always buy a procal or something instead.

 

Thanks guys.
So, part of my reason for doing this would be to keep the steel wheels with my snow tires on them. I guess I would have to get the computer reprogrammed every time I swap.

 

So, next dumb question...
If the diameter is 8.6% bigger, should I expect less performance? (6 speed)

 

buy a programmer and you can reset the computer yourself each time you change the tires.