getting bigger rims = odometer/speedometer changes?

[CASTREX]

Originally Posted by songa

yes that makes sense, thanks. and also, you're right...even after 35,000 miles, you will only be 35 miles off....so say you drive 105,000 miles (close to the end of the life of the car), you'll only be 105 miles off on the odometer...still not that big of a deal. thanks for the clarification castrex!

this brings up one other question...you said that fuel economy will suffer if i get the 17" rims. how much will it suffer, and why? i currently avg around 37mpg. on 17s, will it go down to like the low 30's?

Your MPG drop won't be that drastic. Maybe 2-3 MPG less by going from 15 to 17.

The reason is basically the weight... The weight of the wheels is not simple dead weight. Is spun weight. A wheel is a rotating mass... So that weight has a big impact on the acceleration. If you have a very heavy 17 wheel your engine will have to use more energy to make them rotate. As simple as that.

Another reason is that usually 17 wheels will use wider tires. 205 or 215 wide. That also means more drag. A larger contact area means more friction.

Is all a compromise!

[Ryu]

Originally Posted by CASTREX

Your MPG drop won't be that drastic. Maybe 2-3 MPG less by going from 15 to 17.

The reason is basically the weight... The weight of the wheels is not simple dead weight. Is spun weight. A wheel is a rotating mass... So that weight has a big impact on the acceleration. If you have a very heavy 17 wheel your engine will have to use more energy to make them rotate. As simple as that.

Another reason is that usually 17 wheels will use wider tires. 205 or 215 wide. That also means more drag. A larger contact area means more friction.

Is all a compromise!

^^ What he said.

Also even if you go with 15" wheel, there are some heavy one and light one as well.
Don't get blinded by just the size of the wheel itself.

I found this site quite useful of finding out the weight of the wheel and the weight of your tire as well. Go to any wheel or tire you desired and hit on the spec button.
www.tirerack.com