Reason I'm asking is I'm seriously thinking of getting new wheels to replace my curb rashed stocks. I could repair them, but if newer lighter and smaller wheels = better ride + more mpg I'll spend the $$ for the new rims, cuz mine are ugly. And I think the tires are cheaper too.

Looking at 17x7 (or 8) 40-50 mm 225/50/17

Acceleration and braking improvements are a plus too. Expecting to lose some handling and responsiveness.

 

if the diameter is the same as the stock tires mpg will not change much.

beers

 

Related question, probably the more important one for me to know:

How much heavier will the tire be? Assuming same manufacturer.

 

42 grams

 

same diameter=same MPG
*** for braking, the tire been 225/50/17 the tire will have softer sidewall so less braking
*** for acceleration, if the combination of tire and wheel is heavier, you will loose acceleration

your best bet is to find liter wheel of the same size!!!

 

After more research it is my understanding that the weight savings in wheels, which apparently is only 1 lb, is more or less offset by the weight gain in tires, pretty much negating any performance/efficiency advantage. I suppose the smaller rims would get a smoother ride of course.

Using a smaller tire as well, ie 215/45/17 will decrease the overall tire diameter and mess up the odometer ratings so if there are any mpg savings, can't exactly calculate them. Plus it puts more miles on the vehicle than there actually are. So that doesn't seem like a very good option either. Although this option does save about 4-5 lb per tire. The efficiency gains seem like it would be rather small though since the wheel must rotate more per mile.

Do I have all the facts right? If so, how are the performance gains from smaller rims achieved? Smaller tires as well?

 

Consider this - a narrower tread face (205 vs 225) should mean less rolling resistance for similar rubber compound, tread pattern, inflation pressure.

It will mean cornering performance is decreased though...

 

The difference will be unnoticeable unless you track/autox

I went for a 18lb street wheel with smaller overall diameter tire for street and autox (when not on R compounds), and i felt a difference at first because i wanted to. But i had 3 sets of wheels in my living room all with tires at the time, so i switched back and forth a few times (absolute killer with only hand tools) and found no difference, except that the 18lb wheels and smaller tires are a LOT easier to pick up and put on the car than the 23lb stock wheels with fatter 245mm tires.

The main reason for going to 17s would be smoother ride and cheaper tires. Performance will be worse in all cases.
Normally a doughier tire would have better accel, but this car aint got the torque for it to matter. if you had 400hp and some big fat underinflated tires, yea, youd get some better accel. But without a doubt, handling etc will be worse.

my advice: Get 17's in a cheap allseason or summer for the street. Cheaper rims that look good and easy to clean. Save the money you wouldve spend on 18" tires, and spend that on a set of R compounds which you then mount on your old stock rims. Have your cake and have sex with it too.

 

I think you guys are overlooking the fact that his smaller diameter tires will in turn require greater rpm for the same rolling speed. More rpm = more fuel. Even if the rotating mass is less it will only accelerate better but not get better mpg due to much greater time spent at the new (upper) rpm. How noticeable is it going to be? Hard to say without knowing the rpm difference but it's there regardless.

 

this is the point here.

if you dont know what the dia of the two sets of tires are we cannot help you.

yes weight and width make a difference, but not enough to be enjoyed. the stuff you mention is to close to make a measurable difference.

beers

 

just a curious question. If you change the diameter to a smaller one, is there a way to recalibrate the computer with the new setup without going to the dealer. For example, say you want to run some 17x8 with a 225, 45s on the new, smaller wheels and would lose about an inch in diameter. Can anyone out there, recalibrate so that the odometer will be correct with the new size such as speed/rpm and milage? I have thought about going to smaller wheels myself but, just dont want the odometer to be going faster than it should for warranty reasons. Any know of a person/place that can do this?

 

search yellow box. (google)

then see if you can make it work for us..

also. the software developers have the ability to do if if they can find the area and code it.. (cobb / hymee / others )

or it could be in the abs unit as mm said. then see above!

beers

 

I am not sure where to look. You would think in todays computer age, all one would have to do is to take it to a dealer to reprogram it so that you could just punch in the wheel/tire size and it would adjust anytime you change the new parameters. With todays cars being able to keep track of performance parameters and knowing that people change tire/wheel sizes all the time, makers would just have an input at the dealer that would let you select. For warranty reasons, I can see how it would not be good to let the consumer do it as, you could be running stock tires and put in a larger combo on the computer so that your warranty would last longer. The only option as of now is to document when you changed to the new tire/wheel setup and figure the difference and document. Of course, that would just make the car harder to sell by having an odometer discrepency on the title from there on out. Most just put the new combo on and just let it ride.

 

that might not be to far away. and it will not be a dealer doing it.



beers