wheel weight vs. wheel size.

[StephenB]

What do you think? Is bigger better?
Does anyone have experience testing different sizes?

I am compairing ITR rims in 17 vs 18 and 16.5lbs vs. 18.3lbs respectively.

Thanks for your thoughts and ideas,
Stephen

[Greg Amy]

As long as you can get the widths, offsets, and tire sizes that you want/need, the only wheel diameter you *need* is enough to clear the brakes, suspension components, and body parts.

In other words, a larger wheel diameter, in and of itself, is not faster, and in may ways may even be slower.

GA

[Knestis]

This occurred to me yesterday, car shopping with Mrs. Dr. K. The smallest wheels we saw on among the compact SUVs (CRV-sized) were 16s. Options include 18s.

K

[benspeed]

I selected 16 x 8.5 inch Kodiak wheels for ITR - tires are cheaper, wheels are lighter and I can put down the same contact patch. I think they will be faster than 17s but others may disagree...

[JoshS]

I agree Ben. I'm using 17x8.5 only because the Kosei K1 is available in that size for my car, it's cheap and light. 16x8.5 would have to be custom and would be a lot more money to get anywhere near the weight.

[StephenB]

I selected 16 x 8.5 inch Kodiak wheels for ITR - tires are cheaper, wheels are lighter and I can put down the same contact patch. I think they will be faster than 17s but others may disagree...

Ben, or anyone else...

Are we allowed to run 16" rims in ITR if it only lists a 17 on the spec line?

Stephen

[Z3_GoCar]

Is the spec line wrong? Or did it come with only 17" rims in the US? Can you even fit 16" rims over the brakes? Looks like the only way to fit smaller than 17" rims is if the spec line specifies less than 17" rim sizes.

[erlrich]

What do you think? Is bigger better?
Does anyone have experience testing different sizes?

I am compairing ITR rims in 17 vs 18 and 16.5lbs vs. 18.3lbs respectively.

Thanks for your thoughts and ideas,
Stephen

If you're talking ITR the class, then you're stuck with 17" wheels - unless you're building an RX8, in which case you can use the factory 18" wheels. Generally speaking however, I've always thought that lighter was always better when it comes to wheels, as long as the tire size you want to run are available for that size rim.

[Sandro]

think you need to compare weights with the tires on, because otherwise you are comparing apples to oranges.

[lateapex911]

Larger diameter tires can give you a larger contact patch fore and aft.
But they reduce torque, so you must gear for that. Now, you can often get tires that are lower profile that keep the outer diameter, but allow larger wheels. With street tires, this can be good, as the shorter sidewalls can be more responsive, but race tires are constructed differently, so that's not always a benefit.

But larger diameter wheels and tires can add rotating mass which is hard to spin up and down, so it can hurt accel and braking. Of course, the tires and wheels must be combined to know what you have.

If the overall package is heavier the extra weight is unsprung, so that's bad...worset han if it were equal amounts of ballast. So it's a tradeoff. If you have lots of power and lots of unlimited braking capability, it can be worth it, but generally it's not a 'given' that larger is bigger. In lower hp cars, it's usually not better.

[philstireservice]

I would go with the lightest wheel you can find in your price range. Of course tire price and availablity is a factor.

just another bit of info:

Full tread 205/50R15 RA-1 - 20lbs
4/32nd shaved RA-1 - 18lbs
2/32nd shaved RA-1 - 16lbs
205/50R15 Hoosier DOT Wet - 17lbs
225/45R15 Hoosier R6 - 19lbs
245/40R17 Hoosier R6 - 22lbs

for every 1 lb you save in wheel weight it is like taking 20lbs out of the car.....goes for tire weight also

example 1lb each wheel x 4 = 80lbs

[GKR_17]

Larger diameter tires can give you a larger contact patch fore and aft. But they reduce torque, so you must gear for that.

Larger diameter tires will change the gearing, but will have zero affect on torque.

[lateapex911]

yea, of course, I typed that too fast. But it hurts torque multiplication unless countered with gearing. (However, that can be useful at certain tracks with certain cars)

[Gary L]

Larger diameter tires will change the gearing, but will have zero affect on torque.

Well now, wait a minute...

If you don't compensate for the larger diameter tires by changing some other gearing component, you will shift the entire torque curve to a higher ground speed. Therefore, to say it there is zero effect is not entirely true, IMO.