I wanted to know if anyone had info on what gets you better gas mileage. Narrower, smaller less sticky tires or larger diameter tires? I took off my wheels that had 235/45-17 S0-3's and put the stockers back on (205/55-16). Am i going to notice better gas mileage or will be about the same assuming that my driving habits stay the same. Anyone try this?

 

yes you will get better gas mileage

narrower tires give you better gas mileage as they provide less friction/resistance to the road.

less friction = less energy required = less gas used

 

I think it's coz of the smaller wheels/tires (less rotating inertia = less mass to get moving and slow down = less energy = less gas). Unless he's averaging 100MPH the extra tire width won't amount to much wind resistance.

Not sure the friction is an issue. The only dynamic friction (sliding tires, relative to the ground) is with turning and different slip angles.

I may be talking out of my ... what do I know

 

the lower mass does play into it as well.

friction is always an issue.

 

what about circumfrence? i believe the outer circumfrence of the stock tire is 78.2 inches and the S0-3's have a circumfrence of 79.6 inches?

 

Lighter wheels - less angular momentum so you lose less energy when you accelerate/decelerate.

Narrower tyres - less rolling resistance at a constant speed.

Tyre pressure - keep your tyres pumped up. Low pressure allows the tyre to flex more which loses energy as heat in the tyre.


Whether you will notice the difference going 235 -> 205 is questionable. It might not make enough difference to worry about - let us know

 

i'll check my tank and the mileage over the next few weeks.
overall, im more concerned with the relation between tire width vs. tire circumfrence rather than wheel mass. if it was a case of acceleration i would consider the mass of the wheel a little more.

 

circumfrence does play a roll....small circumfrence = lower gearing. Lower gearing = lower gas milage

weight of the wheels and tires have an effect on it as well though

 

I think tires contribute such a little amount to gas mileage that the way you drive does so much more. When I put my S-03s (225/45/17) on vs my RE92s (or even when I have my PZero on a 225/50/16) so same size width tires, I always got less gas mileage on the stocker size just because I always wanted to push my S-03s harder on turns and such. Also, the S-03s are wrapped around SSR comps, so the wheels do weigh a lot less so mass isn't an issue either.

 

you should definitly change ur driving habits going back to stock tires or you mind find yourself understeering

 

Your stock 205/55/16's make 811.0 revolutions per mile. The 235/45/17 made 796.0 revs per mile. So yah, with your old tires, they were turning less...equaling a lower speed by 1.8%. So your mileage also register lower. If your odo registered 60 miles, you actually travelled 61.1 miles. So ya your gas mileage should be better by 1.8%, excluding friction/pressure...

^ I said that correctly right?

Exactly

 

so what makes a bigger difference? tire diameter or friction?