What's the real story with wheel size and acceleration? - Mustang Evolution

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Old 10-26-2014, 02:53 AM   #1
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What's the real story with wheel size and acceleration?

I read different things from different people online about how wheel size affects acceleration. So, larger diameter makes you accelerate slower right? Some people insist it's only the wheel size that matters, other people say it's the combined diameter of the wheel AND tire. The latter seems to make the most sense to me, would I be right?

I ask because I ordered 18x9/18x10 staggered Saleen style chrome wheels from AM the other day to replace my stock 17x8s and after reading more about it afterwards, I'm a little worried about losing some acceleration. Also, these wheels seem considerably heavier than the stock ones. Stocks are apparently about 17 pounds each. The 18x10 are 31 pounds each, and the 18x9 are 29.6 pounds each. That's an extra 53.2 pounds, or more than half a tank of gas added. On top of that, apparently "rotational weight" makes it affect the car as if it's even MORE than that?

Wonder if I should just sell the damn things locally as soon as I get 'em. That would suck, they would make the car look so good. What to do??
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Old 10-26-2014, 03:37 AM   #2
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What's the real story with wheel size and acceleration?

A larger overall tire is the equivalent of going down in gear.

Example. Going from a 25" tall tire to a 28" tall tire is like going from 3.73s to 3.55s. Forget the wheel size, and look at the tire size, the wheel size is fixed, but with tires you can have different sidewall heights, which is what ultimately matters.

It's not the exact numbers, but that is the principle.

That's why you can't just throw a set of gears at a car and expect it to work, you take in all of the different characteristics of the car and decide the gears and the tires.

Also weight does make a bit of a difference. Heavier wheels you will notice a bit less get up and go, nothing too major though.


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Old 10-26-2014, 04:04 AM   #3
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Thanks, yeah the gear analogy makes sense. They quite literally ARE a gear between you and the road except the road doesn't rotate. Stock tires are 245/45/17... so if I got new tires with a 35 profile on the 18s, I think that works out to something like a 0.6% overall larger diameter. Should feel like a loss of about 1-2 HP. I can live with that.

What about that extra weight though, when you consider it's rotating? That means it's effective weight gets multiplied? These are heavy wheels, this might have a pretty noticeable impact on the acceleration. Damn physics...
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Old 10-26-2014, 05:24 AM   #4
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As a contrasting example to make the point - bought our son an older Jeep TJ on 33" tires that had stock 3.73 gears. The manual tranny was almost useless and no power on the highway, took forever to get up to speed and hard to stay there. Put 4.56 gears in to match to the larger tires and bang - back to stock power or better. Much better at low-gear crawling, too. Installed the compensator for the speedometer, too. If you really want a certain tire and wheel aspect, you can change your gears to reach a target performance goal. Gee, is there an app for this? Plug in what you have today, enter where you want to be with mods/performance, and have it return the mods and parts you need with URLs to the parts dealer
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Old 10-31-2014, 10:48 PM   #5
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Overall wheel diameter is what matters. bigger diameter wheels are like a bigger diameter gear... so transferring the power to the street is harder. ie: the wheel has more leaverage pushing back (fighting the motor). So use a wheel size calculator where you put in the wheel size AND tire size.
Tire Size Calculator - click "Tire Size Comparison Calculator"
Note the percentage differences., etc.

Also wheel weights ARE SUPER important. Anyone who tells you different doesn't know jack. Lighter wheels accelerate quicker, brake easier, handle better (they bounce up & down to hug the road more freely), the advantages of lighters wheels are HUGE.

Look at really high performance (expensive) vehicles they ALL use high quality forged, lightweight wheels. The other day I was looking at the Camaro Z28 page, and the Z28 uses wheels that are like 40 lbs (10+ lbs per wheel) lighter than stock Camaros. HUGE DIFFERENCE.

I just upgraded wheels and that was the first thing I looked at.. wheel weights, then pricing, then appearance. If they weren't lightweight, I kicked them out (ie: no cheap replicas), then they had to be in budget, then I picked the appearance I like the best out of what was left.
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Old 10-31-2014, 10:52 PM   #6
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Quote:
Originally Posted by c_rizzle View Post
Overall wheel diameter is what matters. bigger diameter wheels are like a bigger diameter gear... so transferring the power to the street is harder. ie: the wheel has more leaverage pushing back (fighting the motor). So use a wheel size calculator where you put in the wheel size AND tire size.

Tire Size Calculator - click "Tire Size Comparison Calculator"

Note the percentage differences., etc.



Also wheel weights ARE SUPER important. Anyone who tells you different doesn't know jack. Lighter wheels accelerate quicker, brake easier, handle better (they bounce up & down to hug the road more freely), the advantages of lighters wheels are HUGE.



Look at really high performance (expensive) vehicles they ALL use high quality forged, lightweight wheels. The other day I was looking at the Camaro Z28 page, and the Z28 uses wheels that are like 40 lbs lighter than stock Camaros. HUGE DIFFERENCE.



I just upgraded wheels and that was the first thing I looked at.. wheel weights, then pricing, then appearance. If they weren't lightweight, I kicked them out (ie: no cheap replicas), then they had to be in budget, then I picked the appearance I like the best out of what was left.

Koenigsegg uses Carbon fiber wheels. You can pick the whole thing up by a finger.


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Old 10-31-2014, 11:26 PM   #7
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Yeah, I should have looked at weight first I guess. I really liked the Saleen look though, I'm not sure if I would have been very happy with something else. It just kind of looks right on the New Edge body to me. I got them installed tonight anyway. On the plus side, the new tires are a bit lighter than the old at least. I can notice a difference in acceleration, but it's not that bad. I'll probably get some 3.73s put in soon to (more than) make up for it.

Thanks for all the clarifications. I'll take some pics tomorrow when the sun is out. I think it looks pretty good. The chrome finish on these AM wheels shines more than I expected.
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