Narrower tires on stock 17" wheels?

[bobbyc03]

Hi,
It's time for some new tires. The continental 245/75-17 tires have worn down quite quickly. The local tire shop we use for our other work vehicles sells cooper tires.

I was wondering the pros/cons of asking for 235/80-17 tires. Our f250 reg cab is auto 3.73 axle, and 4x4. If they'll fit on the wheels, what do you think?

Pros:
*Narrower tire (maybe better MPG?)
*Taller tire (lower RPMs on highway?)

Cons:
*Speedo will be off until we can get the dealership to adjust the CPU to say 18" wheels?
*Spare tire wrong size

Thanks,
Bob C
PS, the truck never sees towing or heavy loads; just carries around tool boxes/ladders.

[bobbyc03]

Wow,
I did some research and the overall diameter isn't much different. 31.65" from 31.5"... almost not worth it.

I also think the rim would be almost too wide for narrower tires.

Thoughts?

Bob C

[timid1]

Originally Posted by bobbyc03

Hi,
Cons:
*Speedo will be off until we can get the dealership to adjust the CPU to say 18" wheels?

You lost me on 18 inch wheels?

[bobbyc03]

The dealership can adjust the cpu in the truck to adjust for tire differences. The cpu has all the stock wheel/tire sizes that are offered on new trucks, from 17", 18", and 20"

I ran some of the online tire size calcs, and there is barely any difference between 235/80-17 and 245/75-17. Before, I was thinking that the difference might be substantial, and I'd have to have the dealership adjust the cpu.

Bob C