My future wheel setup will be my stock Goodyear tires stretched onto 15x8 rims. Correct me if I am wrong, but it seems to me that stretching the tire will reduce the overall diameter of the wheel/tire package...which would in turn cause the speedometer to read higher than the stock setup.

Curious if anyone who has stretched their stock tires onto a 15x8 rim have experienced any issues with accurate speedometer readings. If so, what is the fix? I'm wouldn't be as concerned about the speedometer as I would the mileage climbing at a faster rate.

Thanks for any insight you may be able to provide.

 

http://www.miata.net/garage/tirecalc.html

 

Thats helpful but does not take into account the stretch of the tire.


I have 195/55/15 on my 15x8s and I do not notice a change in the speedo. 195/55 is almost the same exact size as the 185/60s that come on the car as far as overall size. The stock speedo is off by alot most of the time anyways. Mine was off 3 mph from what my Nav say it is.

 

Exactly what I needed to know. Thanks for the info.

 

You probably wouldn't notice a change in the speedo as I believe that the speed is based on a gear drive in the transmission. This very common with fwd vehicles these days.

Tire size has ZERO effect on what the cluster shows.

Doesn't matter if you have 13's or 22's. 60mph @ 3000rpm is 60mph @ 3000rpm.

edit: The vehicle's actual speed will be different though.