Ok, I admit I have no clue why one wheel size would perform better or be more desirable than another. Bigger rims look cooler to me but up to a point. For me no larger than 19" on the current car. I get the larger the wheel and tire, the cost can increase dramatically. But I've read several post's that perhaps an 18" wheel on this Mustang is the better performer. Can you guys weigh in on this for me?

 

I'm no expert but generally speaking the large wheel matched with thin tires is the current style trend. I'll assume its to diminish the gap between the fender well and tire without lowering the car but some do both for the totally slammed look.
I think its safe to write, that performance suffers from larger wheels due to the added weight, unless your shopping race-spec lightweight wheels. I believe the general rule of thumb is the larger the wheel, the thinner the tire, so reducing a tire's sidewall leaves you closer to the road, so you feel more and whether or not that's a good thing is up to you.
My 1985 Gt has stock wheels and THICK tires and its floats smoothly over any surface, my 05 has 18's with thinner tires, I feel more connected to the road but sometimes its a hassle. My 2011 GT/CS will have 19s with a moderate sidewall width, from my experience I'll keep it stock.

 

I run the factory 18's for daily driving duty, but for racing I run 17's for reduced weight. Doing so saves me 22 lbs of rotational mass. Not an earth-shattering difference, but rotational mass is the performance equivalent of twice as much static weight (that doesn't rotate), so it's like taking 44 lbs of non-rotating weight out of my car.

 

if by performance you mean "handling", then a shorter sidewall with less flex will perform better

if performance means drag racing, then a taller sidewall from using a smaller diameter rim will flex a little more allowing the sidewall to crinkle thus giving better traction - especially when running lower air pressure

and like others said, rotational mass
it's easier to get a tire spinning if it's smaller in diameter and lighter

remember Newton's Laws
a body at rest tends to stay at rest
a body in motion tends to stay in motion

 

Its also used to balance the design of the car and make it look less bulky, but I suppose its part and parcel with which came first; the chicken or the egg.

I guess somebody could argue that the desire for big wheels drove vehicle design in a certain direction and without those big wheels the cars would appear ponderous (just look at the GAC F5 Camaro running 245/45R17's IIRC).

 

I have no experience in racing so I'm no expert. I wonder, though, if there are diminishing returns with a shorter sidewall. Going from 70 to 60 series is huge, I'm sure. Going from 60 to 50 is still significant but probably not as significant as going from 70 to 60. Given that real world roads are not racetrack smooth, at some point does an ever shorter sidewall become a liability to handling? The tire sidewall serves as a shock absorber and when it's very short -- say 40 or 35 series -- it's doing very little shock absorption. This probably results in the car being shaken a lot more and I wonder if this doesn't have an overall negative effect on handling. Hopefully someone with more knowledge than me can verify or refute my theory.

 

Car and Driver had an interesting article on this in the latest issue.
http://www.caranddriver.com/features...sted-tech_dept

 

Interesting article, maybe I should have stuck with the 18 inch wheels?

 

Well, not exactly. I think the biggest issue is that you really don't want to go below, say, a 40-profile tire. In the article, the 18-inch wheel was a 40 profile. I haven't checked the 2011 tire sizes, but on the 2010 GT, the 19" wheels come with a 45-profile tire. In the article, the 17" tires on the V-dub were a 45-profile tire, so you can expect decent performance.

Ultimately, a GT on stock 18" wheels will have a somewhat more compliant ride and the 19" wheels will offer the better handling. IMO, you made the right choice.

 

Well, there was virtually no difference between the 18 and the 19 in that article.

And, here is an article that showed that heavier wheels (same size) went faster than lighter Volk/SSR wheels.
http://www.modified.com/tech/modp-09...est/index.html

In either case, I don't think it is even noticeable.

 

True, but one of the heaviest wheels also performed the slowest as well. I think the wheels that are in comparison are to close in specs to each other to actually make a huge difference.
For me a good comparison would have been if they would have thrown in a stocker 18x8.5 that weights in 27lbs like on the Mustang and test a against a much lighter wheel.

 

Remember this was with a VW Golf weighing in well under 3k lbs. A heavy car like the Mustang 19's are fine, the reason why people choose 18's is there is a larger tire selection. Although, 19 inch sizes are getting plentiful as well.

Dave

 

OK, thanks guys!

 

I have always wondered if the reason bigger rims and tires weigh more is because the manufacturing process of the wheel is not as high tech.
My reason for this thought process is that when you add an inch to a wheel, (going from 17" to 18"), you extend the "spokes" an inch, but lose an inch of rubber on BOTH sides of the tire, thus making the tire lighter. Wouldn't that make up for the extra inch in the spokes?

 

You can get a great set of 19's that weight as much as the OEM 18's or less, but you are going to pay

 

I read a test in magazine a few months ago (can't remember which one). It had to be on a Mustang because thats all i've been reading for the last few months. In the test they said they got better steering feed back and road feel with the 18 inch wheels and tires than with the 19 inch wheels and tires. I read this several times because at the time i was thinking about buying a 2011 G.T. before i changed my mind and decided to buy a V-6 instead.
I would have thought it would have been the other way around.

 

No, the tires don't get lighter. Research major manufactures and you will see weight will stay similar, may go up a few lbs too.
Good handling tire is up to the tire, not so much being a low-profile. How many F1 cars are on dubs?

 

better looks with the 19s and unless you are stripping it down to be a track car you will appreciate that much more on an everyday basis.

 

Were the tires the same (brand, model)? If not, that could account for it. Tires make the most difference anyway.

 

The diameter of a 19" wheel is larger than an 18" and thus more metal and more weight.
Tire weight doesn't change that much with the sidewall reduction -- most weight seems to be in the tread.