I have just changed from 16 alloys wheels to 17 polished wheels. First is there going to be an appreciable error in the speedometer? And what is the correct tire preassure for the 17 Firestone wheels? Thanks in advance for your imput.

Your Dealer can reprogram your computer for that size wheels, I used to keep between 34-35 psi, With nitrogen.

The wheel size dosen't really matter it's the circumference of the tire. If the diameter of the previous tire is say 29" on a 16" wheel and the 17" wheel is mounted with a tire that is 29" in diameter than there is no difference. I have a car with 16" wheels on the back and they have a diameter of nearly 31" but the tires on my HHR with 18" wheels are way smaller at maybe 27" due to the aspect ratio of the tires.

If you put on the same size tire as what comes stock on the 17", there shouldn't be any need for adjustment. As for air pressure, if you like a little softer ride then maybe the lower 30s, for a bit harsher ride then mid 30s.

COrrect, it's the height that may throw off your speedo. If the height is the same no worries. If they are different, the ECM can be reprogrammed to correct.

Air pressure, stick with what the factory recommends. Changing the tire size does not effect that. Pressure is still pressure (don't go over what the tire lists as max). As far as nitrogen... not needed on a street driven family vehicle. Unless someone can produce facts that state otherwise.

As far as nitrogen... not needed on a street driven family vehicle. Unless someone can produce facts that state otherwise.
Sorry for the insert about Nitrogen,,was not pluggin for it that is in other threads!
I was just making a statement as to what I had in my Stock 17" tires as well what in my 18" tires.
Thank you again for the schooling.

Sorry for the insert about Nitrogen,,was not pluggin for it that is in other threads!
I was just making a statement as to what I had in my Stock 17" tires as well what in my 18" tires.
Thank you again for the schooling.


That's fine, just didn't want the OP to think it was actually needed.