I would really like to go with some aluminum 15" rims on my CRX HF, but I don't want to add rotational weight which would have a negative effect on my fuel economy. I've got the factory 13" steel rims with 175/70R13 tires. I'll weigh these in a few days to determine what base weight I'm working with.

My question is this: can a larger rim and tire combo be lighter than the smaller rim and tire? I'm hoping it would be possible with a minimalist (i.e. 4 spoke) aluminum rim and fairly low-profile tires.

 

It really won't affect your fuel economy. You won't notice it.

There are a lot of other factors involved that I won't get into.

 

D'oh, I completely forgot about the difference between the amount of energy needed to keep a rotating mass in motion vs that needed to set it in motion. If it was all around-town driving I might notice the difference (especially with 64HP of motivation), but since most of my driving is a highway commute it shouldn't be a big deal.

I'm more likely to notice the difference in braking. I'll have to see what it takes to change from the 9.1" to 9.5" rotors up front and maybe go disc in the rear. I have to re-do the brakes anyhow, so if it's not much more expensive I would consider it.

Thanks Old Man Neri

 

Ya there is also the whole thing about where the mass is in relation to the centre. A 13" wheel might have more of it closer to the centre than a 15". It is possible to have a wheel weigh more but have less rotational inertia.

In the end it still not going to matter much. Probably equivalent to you taking a dump before you get into your car. I suppose if you really want to save weight you could drive around with just a half tank of gas.