Rim size vs. Performance

[Lunch_Box]

Hi I was wondering if someone can explain to me how getting a bigger diameter rim affects performance. I kind of understand it but what I dont undestand that if you have a 16" rims and stock sized rubber why that would peform better than a 18" or 19" rim with smaller rubber. Both sets will have the same overall size so can someone tell me why the smaller rim is better for performance. Also if you have a car with 17" rims how much time in the quarter mile would you lose if you went with a 18" or 19' rim on the exact same car?

 

[fatafall]

The 16" rim would have tires with a bigger sidewall that would help the performance as far as cornering goes and the bigger wheels hurt your ET in the 1/4 because the bigger they are, the more they weigh (generally) and more weight equals lower ET. Thats what I have heard and it makes sense to me, but you never know, feel free to correct me.

 

[trapspeed]

Hard to say. I think 19s are too big on Eclipses anyways..

18s if you can't live without a little bling factor.
17s if you are more performance oriented.

I had 18" Motegi MR7s before. They looked alright on the car, bigger wheels tend to always look better in my opinion. But damn were they heavy, 27.5 lbs per rim!!! I don't know if I was playing mind tricks but when I switched to my 17" Rota Subzeros (16.5lbs per wheel) I could tell a difference in performance, somewhat in acceleration. I mean don't get me wrong, 17" rims look good! Plus you save a few hundred. I'm happy with my 17s.

 

[saw wave analog]

bigger rims are heavier, more rolling weight means the drivetrain has to work harder to do the same amount of work, plus you will get less accelerating traction with an inch of sidewall vs 3 inches

 

[trapspeed]

I heard bigger rims = better mileage.

 

[Lunch_Box]

Okay I can understand the bigger rims being heavy theory. But what if you have a set of forged rims like volk or a similar company where the 18" or 19" weigh as much as a set of 17's. Is there going to be any difference in performance then?

 

[trapspeed]

Doubt it.

 

[pinknuggit]

larger tires are the equivalent to putting a lower final drive gear ratio in your car. That's why it makes you slower because it's like swapping in lower gears.
That's why most drag wheels range from 13" to 15". The smaller tire means your wheel will spin faster for each rpm of your engine vs. stock so you will have quicker acceleration but you will not have as high of a top speed.

 

[Lunch_Box]

Yes but most 13" to 15" drag tires have a bigger side wall on the tire so if a 15" rim and tire are the same size as a 19" rim and low profile tire how would that make a difference.

 

[2gGSX]

I heard bigger rims = better mileage.

no, more rotational mass = less everything
For strict drag racing, a smaller rim + tire with massive sidewall will be best.
For the rest of us, 17" is the consensus for best performance, since 17x8 rims let you fit 245 width tires and massive brakes, as well as lowers the profile of your tires which decreases sidewall flex and thus raises cornering potential.

 

[InferiorWang]

^^^
thank you. someone finally said rotational mass. When you have larger (and generally heavier rims) it takes more power to get them moving and stop them. The further the weight is to the outside, the harder it gets. That's why if you could find a 19" and a 16" rim at the same weight and put tires on to compensate for sizes, the 16" is going to be easier to turn.


Then, when you have smaller rims and larger tires, the tires give more and get you more traction for dragging. However, having rims a little bigger with a smaller sidewall gives you better cornering traction. IMO, and the opinion of a few others here, 17s are the best compromise for dragging, cornering, and just looking better.

 

[Lunch_Box]

Thank you for clearing everything up. That all makes sense now.