Bigger wheels + better tires = better performance?

[Power4]

I've been contemplating what wheels and tires to get and I'm wondering if I get bigger wheels and better tires than my stock ones if I could expect better performance out of the car? Obviously getting better tires than the stock Pirellis I have now will increase grip and in turn make for somewhat better acceleration and handling, but will it be noticeable? I currently have the stock 17x8 bullitts with Pirellis with about 20,000 miles on them. I'll probably get 18x9s with Kumho Ecstas.

 

['69 Hardtop]

Better handling, yes. Better acceleration, maybe but probably not. Larger wheels and wider tires increase the rotational mass of the wheel. More mass requires more power to turn them. So expect some reduction in your get up and go. Wider tires also increase the "foot print" and therefore less lbs/sq in. on the ground and tends to make them easier to spin (although some tread patterns are better than others at reducing this).

 

[walter]

Bigger doesn't necessarily mean better... Unless you're buying lightweight wheels you'll most likely see a performance decrease in the acceleration and handling. Also I seem to have noticed that while cornering ability increases with a wider wheel the handling suffers. The car may be able to physically pull more G's on the skidpad and ultimately more speed through a turn but your steering feel will suffer as the wider tire will numb and slow the wheel action down.

That's why for AutoX the stockers will make the car zip around the cones and for trackday/street the aftermarkets go on.

 

[gashog]

Power4,

I've learned that better tires are the best handling upgrade... period. I noticed a world of difference going from all seasons to summer tires (previous ride) Night and day.

Wider/bigger tires like mentioned above increase rotational mass and it is noticeable if you make a huge jump. With my new wheels on the stang, I noticed leaving the parking lot from the tireshop that there was a little bit gone (albeit very tiny) from the acceleration going from 17" to 18" wheels.

I haven't really got on the new BFGs because tirerack recommends the first 500 miles be easy. But I can already feel the stiffer sidewalls, much more responsive even in normal driving.

I would reconsider the Kuhmos, I had a set of those and they were noisy as hell after about 10k... just my personal experience. Granted, that was a few years ago and maybe they've improved, but I will never buy another set from them again.

 

[Mr_Q]

Bridgestone RE050A
Bridgestone RE-01R
Dunlop Direzza Sport Z1
GY Eagle F1-GSD3

Any of those above tires will make your car a handling demon. And if you go with a not so aggressive profile (45) the ride qual won't be so harsh for daily driving.

All the tires will be noisier than stock, so be aware. The price of performance.

 

[o0Dan0o]

Wider tires also increase the "foot print" and therefore less lbs/sq in. on the ground and tends to make them easier to spin

Thats not true. Tire width has nothing to do with total contact area, that is soley a product of the weight the tire is bearing and the pressure of the air in the tire. If the tire is at 40 PSI and the load on the tire is 875lbs than the contact area is 21.875 square inches. Drag racers reduce tire pressure to increase the contact patch and because rubber's coefficient of friction is reduced by pressure (the lower the pressure the higher the coefficient).

A wider tire is better to an extent (due to not so well understood dynamics), and given the weight of our cars that should go beyond 275s. But like has been said, you want to find a wheel that is as light or lighter than the wheels you are replacing.
Dan

 

[Power4]

So if I understand you guys correctly getting bigger wheels is only detrimental to acceleration but with nice sticky tires it can improve handling noticeably? My goal is to improve the car's handling anyway before I think about getting any serious power upgrades.

 

[Hoboattacker]

It wont necessarily be a detriment to your acceleration. You wont spin as much. It will just hook and go so actually, you might accelerate faster. But yes, it does improve your handling, too.

 

[1hOtStAnG]

I've been contemplating what wheels and tires to get and I'm wondering if I get bigger wheels and better tires than my stock ones if I could expect better performance out of the car? Obviously getting better tires than the stock Pirellis I have now will increase grip and in turn make for somewhat better acceleration and handling, but will it be noticeable? I currently have the stock 17x8 bullitts with Pirellis with about 20,000 miles on them. I'll probably get 18x9s with Kumho Ecstas.

I have 18x9 and 18x10 Boyds on my car with BFG G-Force KDW tires and the feel of more rubber in contact with the road is very noticeable.

 

[Rebel73]

with my stock 235/50/18 BF Goodrich KDWS and my HO Whipple, it feels like I'm riding on ICE.

I needs some fatter rubber soon!!

 

[gashog]

So if I understand you guys correctly getting bigger wheels is only detrimental to acceleration but with nice sticky tires it can improve handling noticeably? My goal is to improve the car's handling anyway before I think about getting any serious power upgrades.

A lot of it has to do with the sidewalls as well. If you have a thinner, stiffer sidewall its less likely to flex and the car will handle more firm as well as ride rougher. The softer tire the stickier it will be too. If you can get away with throwing summer tires on there that will make the biggest difference. High performance all seasons have nothing on high performance summer tires.

 

[stangdude2000]

Its all in the tire compound. The softer, the more grip you will have for both accelleration and cornering. As people have mentioned, bigger/wider = more rotational mass. Even if you have two wheels that weigh exactly the same, if one has more weight that is farther away from the axle, it'll perform worse than one with mass closer to the center.

 

[91frppgt]

when i switched from my 18's to 20's i noticed no performance lost whatsoever!
actually, at the track the 20's hooked harder! 1.88 60'. I couldn't pull no 1.88 with the stock BFG's...

 

[SoCal89GT]

Ok, there has been some fact and fiction in this thread and I would like to clear everything up so you can make the correct choice on what you want to buy.

1. Wheel Diameter: As has been said previously, the larger wheels are typically heavier and in being such are a larger rotational mass to get moving--- this hurts performance. However, many A/M wheels depending on how much bigger you go are actually lighter than the stockers. With the rim diameter and tire diameter being larger you will feel a loss in off the line acceleration because you are changing the gear ratio. It would be the same concept as if you had 4:10's in the rear and went down to a 3:73 type feeling because you are reducing mechanical torque multiplication with the larger diameter.
2. Wheel Width: THE WIDER THE BETTER! unless you are going for gas milage, the fatter the meat, the better the traction... period. You will not see any hinder to handling, the only negative that can be seen is that if you have a lot more grip in the rear than the front then you may see a gain in understeer which tends to be an issue on the 05+ mustangs.
3. Tire Sidewall: The lower the profile, the less deflection and roll of the tire under cornering<--- This is a good thing. You will definatley see a ride qulaity loss with the lower profile tires depeding on how low you go. But one thing that I do know is that Ford went with tall tires to comply with the NVH constraints.
4. Tire Compound: It was said above, and I agree 100% that tires are the biggest factor without any doubt. If you go from a factory all-season to a Max Performance Summer tire, you will feel as though you bought a new car. Add that to a slightly wider and lower profile and you will be extremely happy with the performance gain. And if you go with a softer (stickier) compound then they will hook up better and you will probably see increased 0-60ft times in the 1/4 mile, especially if you are upgrading from stock, even if you increase wheel diameter.

I am and Engineer and I can back up everyone one of these statements with books if you dont beleive me. I am not trying to be a A-hole or saying that everyone else is wrong, i just want to put it all together as clearly as possible for everyone.

 

[DarkFireGT]

I will say that going from the stock 27" wheel/tire combo to a 28" drag tire, I was able to hit the same ET at less MPH. What that tells me is that I'm accelerating slower, but I'm hooking up better. I was also babying a burnt clutch, though.

 

[Hoboattacker]

Ok, there has been some fact and fiction in this thread and I would like to clear everything up so you can make the correct choice on what you want to buy.

1. Wheel Diameter: As has been said previously, the larger wheels are typically heavier and in being such are a larger rotational mass to get moving--- this hurts performance. However, many A/M wheels depending on how much bigger you go are actually lighter than the stockers. With the rim diameter and tire diameter being larger you will feel a loss in off the line acceleration because you are changing the gear ratio. It would be the same concept as if you had 4:10's in the rear and went down to a 3:73 type feeling because you are reducing mechanical torque multiplication with the larger diameter.
2. Wheel Width: THE WIDER THE BETTER! unless you are going for gas milage, the fatter the meat, the better the traction... period. You will not see any hinder to handling, the only negative that can be seen is that if you have a lot more grip in the rear than the front then you may see a gain in understeer which tends to be an issue on the 05+ mustangs.
3. Tire Sidewall: The lower the profile, the less deflection and roll of the tire under cornering<--- This is a good thing. You will definatley see a ride qulaity loss with the lower profile tires depeding on how low you go. But one thing that I do know is that Ford went with tall tires to comply with the NVH constraints.
4. Tire Compound: It was said above, and I agree 100% that tires are the biggest factor without any doubt. If you go from a factory all-season to a Max Performance Summer tire, you will feel as though you bought a new car. Add that to a slightly wider and lower profile and you will be extremely happy with the performance gain. And if you go with a softer (stickier) compound then they will hook up better and you will probably see increased 0-60ft times in the 1/4 mile, especially if you are upgrading from stock, even if you increase wheel diameter.

I am and Engineer and I can back up everyone one of these statements with books if you dont beleive me. I am not trying to be a A-hole or saying that everyone else is wrong, i just want to put it all together as clearly as possible for everyone.

Wider is not always better. I don't care what your book says. You go to wide and you lose any gain that there was in traction with a massive loss in acceleration. You want to go with a wide enough tire and enough sidewall, too. For the most part, the more sidewall, the better for drag racing. You want your tire to be able to FLEX. If it's just hard and rigid, you will spin no matter how wide your tire is. There is a balance between width and sidewall height that is best, you just have to find what is best for you.

 

[SoCal89GT]

Ok, you are taking this out of the context in which i was referring. Power4, who started the thread said that he was more concerned with handling right now, more than the acceleration as he was going to worry about that later on.
BUT... you are correct if standing launches and straight line acceleration were your priorities. Drag slicks always have a larger, softer sidewall for a few reasons.... The softer sidewalls will act as additional springs functioning in series with your rear chassis mounted coil springs and will hopefully soften the overall spring rate in the rear. This then aids in weight transfer to the rear adding to mechanical grip and therefore more rear traction. I can go on further if you would like. Also, drag tires are also run at a low psi because they will have a larger contact patch with the track and as the torque transfers to the ground, the tire will flex and deflect torsionally rather than the than just spinning.
As far as wider being "a massive loss in acceleration" I dont know how you come to that conclusion. If you are referring to the weight gain that hurts more than the traction adds, you are wrong. The percentage gain in weight in negligible with the wider tire in comparison to the percentage contact patch area gained which is gained traction. Especially in 05+ mustangs where the issue is not available torque or power, the car is traction limited at the rear. This may be more arguable with a smaller, light car that has much less power such as a Miata or even a Lotus. Please fill me in as how you arrive at your claim... also consider that drag slicks are ALWAYS wide as i have never seen a skinny drag slick on drive wheels, so your statement is saying that professional NHRA teams and tire manufacturers have it all backwards if i am understanding you correctly.

 

[o0Dan0o]

If you are referring to the weight gain that hurts more than the traction adds, you are wrong. The percentage gain in weight in negligible with the wider tire in comparison to the percentage contact patch area gained which is gained traction.

The contact patch area does not increase with wider tires, thats a matter of tire PSI. Other than that, I generally agree.
Dan

 

[SoCal89GT]

The contact patch area does not increase with wider tires, thats a matter of tire PSI. Other than that, I generally agree.
Dan

I do not agree... by this logic a bicycle tire with 10 psi has a larger contact patch than lets say a 275 with 30 psi.

I will agree though that tire pressure does factor in to the contact patch area but if you were to calculate the area it would be a function of tire width, diameter, tire pressure, and load.

 

[o0Dan0o]

I do not agree... by this logic a bicycle tire with 10 psi has a larger contact patch than lets say a 275 with 30 psi.

I will agree though that tire pressure does factor in to the contact patch area but if you were to calculate the area it would be a function of tire width, diameter, tire pressure, and load.

Tire load divided by PSI gives contact patch area, give or take. Theres a lot more to it, obviously, with how the sidewall and tire core react to being deformed, but that should only make minor differences.
Dan