Alright, I want to upgrade from stock 205/55/16 tires and rims to 215/45/17 tire and rim combo. I am worried about screwing up the speedometer and losing low end torque from going from a 16 to 17" rim, but on the 17", I am actually going down in sidewall tire height from 55 to 45. Therefore won't the rotational mass on both wheel combos be exactly the same?

 

215/45 and 225/40 will both result in less than 1mph difference on the speedo. 245/40 will result in I think a little over 1mph difference (all differences measured at 60mph). www.discounttire.com has an easy to use tool to calculate the change to the speedo.

 

1 mph off on the speedo I can live with. Just wonder what torque and gas mileage affects it will have. Thanx for the reply!!

 

depending on what wheels you're getting, you should see a slight increase in acceleration and also slightly better MPGs, if the wheels are lighter than stock. You won't however see an increase in measureable torque, just less inertia for the torque to overcome (although i may be wrong about that)

 

Probably go with Rota tarmacs or Subzeros. I understand these are pretty lightweight.

 

When your speedo is reading 60mph, you would actually be going 59.4mph.