Wheels: How Big Is Too Big..?

[MilesSpeed]

It's obvious that 15-inch wheels aren't ideal for grip, and that larger diameter wheels paired with better technology in the tires can help keep sidewall flex down without loosing compliance.

Where is the line? When does the lack of side wall flex cause loss of traction?

I am looking to get together information to help advise people so they aren't shocked with their $3,000 20s don't handle as well as their 17s.

Does anyone have any input? Any cool diagrams showing sidewall flex? Personal stories about this first-hand?

Any input is appreciated!

[Vegas69]

17's are probably the best if you still want to fit good brakes.

['JustDreamin']

It's obvious that 15-inch wheels aren't ideal for grip

I wouldn't immediately jump to that conclusion, since there are alot of race cars running 15" wheels. Some of that is mandated, some of that is by design. There are probably many vehicles out there that perform best with 13" wheels or smaller (say Formula SAE or something along that lines).

The biggest problem with 15" wheels on a typical musclecar is the lack of space for adequate brakes for the weight of the average vehicle (at least IMO).

It strikes me that every vehicle is a different compromise, depending upon the owner's desire, and that the answer is different for every car. But, I'd say 17 or 18 is the top end of the window. Beyond that, the gains in rotational inertia are just too great. 22's are funny to look at, and much tougher to start and stop. I think a comparison of the physics involved would be interesting (say an Excel spreadsheet) and it would be great to have somebody do some testing to verify that the math works. Has the possibility of being a neat magazine article (IMO).

The ceramic 15.5" front rotors on the '09 ZR1 are really neat and cutting edge, but I wonder what they weigh & cost. And the 19" rims that are required to fit over those rotors (and calipers) certainly put alot of aluminum an awful long way from the center of the spindle. I would be interested as to how a similar, yet smaller sized set of rotors (and wheels) would work on the ZR1.

[fastback]

Wheels:How Big is Too Big..?

[brownz]

^^ HAHA what a idiot

[Mr.VENGEANCE]

and i wouldnt say the 20s are out of the ballpark so fast yet either..

but yea.. it all depends on your suspension setup...

[TonyL]

There's plenty of threads here already on the subject Liz, but to paraphrase them, it comes down really to brake clearance and rotating mass issues. There's a fine line, right at the 18" mark where the rotating mass of the wheels becomes a bigger detriment to performance than the gain of the lower sidewall, and resistance to flex. Plus, you have to take into account the lack of good R compound tires available for wheels in excess of 18" They just don't exist.

[Vegas69]

Not true....19's are available now.

[TonyL]

I stand corrected. However, I'm sure that extra inch of rotating mass costs more than any performance gained.

[1969CamaroRS]

17s I think is where the sweet spot is. Just big enough to clear big brakes and get modern tires. Anything else is just adding rotating mass. Unless you are going monster brakes that won't fit 17s, no performance reason to go bigger, aesthetics aside.

I do see what some people say about 18"s fitting the wheel wells on our classic cars better, but to me I think a little bit more sidewall looks better than a slightly bigger wheel, imho.

[ProdigyCustoms]

Besides the Moment of Inertia issue with larger wheels / tires. There is the issue with not being able to get enough sidewall on a 20 and get it under many cars. Take a Camaro for example, the most tire you will get under it if you lower the car is a 27" tire. Which is only 3.5" sidewall. Go to a 19 and 27" tire and a 4" sidewall which is much better. Still a greater Moment of Inertia, but better none the less in all ways then the 20.

But with that said the new Vipers and ZR1 Corvette come with 25 series tires on 20" wheels

[MrQuick]

I'd go with 18's max....20's are just silly.

As long as they are light I don't see any other problems.

[Young Gun]

For a while I was planning on running 20s in the back and 19s up front. I started looking through wheels and the difference between 20s and 19s as opposed to 18s all around was close to 600 bucks for the wheels alone and I don't even want to think about the difference in the cost of tires... When it comes down to it, I think I definitely benefit front the larger sidewall as well as the greater selection of tires available. I can still fit large breaks behind 18s and I do not lose any of the aesthetic appeal the wheels offer. The best part? I do not have to hear my stupid friends saying I am riding on "dubs"

[Roadbuster]

The rule of thumb is to have the wheel diameter just large enough to clear the brakes and suspension. I went with 18s vs 17s since I could get a taller tire, and could clear more of my front suspension. The extra inch in diameter did not help me clear the shock mounts in the rear over the 17s but it did let me get a tire that really filled out the rear wheel well.

To sum it up: don't go any larger with the wheels than you have to.

Jon

[WILWAXU]

On a true corner carving muscle car, 18's are probably max, mostly limited by suspension design.

Once you jump above 18's you need a suspension specifically design to use them, i.e. new Vette's, super cars, etc.

[chicane67]

Largest practicle ?? 18"

But it is true... 17's do have a sweet spot with a first gen's wheel base.

[Sparky67]

The ceramic 15.5" front rotors on the '09 ZR1 are really neat and cutting edge, but I wonder what they weigh & cost.

Here is a post on how much the new Carbon Ceramic Brakes cost.
http://www.leftlanenews.com/brembo-a...sc-brakes.html

Jeff

[MilesSpeed]

thanks for all the great input guys, can anyone tell me why NASCAR runs small wheels still?

[MilesSpeed]

That is REALLY too big, and even worse, 3 spoke!

[TonyL]

because they work. It's one of those "if it aint broke dont fix it" things.

Rapid changes in sidewall deflection don't happen when you are constantly turning left.