Will larger rims slow a car down?

[Myasylum]

Just wondering if anyone has done a study on this? I have 15x8 Stock(ish) steelie rallye rims at the rear now (center caps and trim rings and 275/60/15 Tires), but spin pretty easily, thinking about getting 15x10 rims with larger tires for better traction, however would that extra weight slow the car down?

Or would an aftermarket Aluminum rim be better if they are lighter weight? Perhaps, the difference is so miniscule it doesn't really matter? IDK? This is why I ask.

Any opinions on this?

Thanks!

 

[hdwrench]

i’m no scientist but was taught long ago , any reduction in un-spring weight is good for speed & acceleration…

 

[BLK 68 R/T]

I doubt you would notice a difference provided you are sticking with the same diameter of tire.

 

[gkent]

Not unless the rims are solid lead and the tires are filled with concrete !!

 

[R413]

YES absolutely! Go to the tack and get a time slip. You can see and feel the difference. Those 8" wide steel wheels are 30-32lbs EACH. That is a ton of weight, and it's not only unsprung weight it is rotating weight.

Car Craft magazine in early 80's did a drag test on a car with 15x8" rallies, then some aluminum wheels like weld wheels or center lines. It was 2 thenth's and 3 mph. The car was a small block chevelle street car.

now the post #3 that said you may not notice the difference is true, many won't, and the illusion of winder tires and more performance is real. BUT, that doesn't mean it won't be happening and you don't know it.

Now how about the effects on the braking with heavier wheels and tires? That's a real thing also.

I have a computer spin balancer at home and you close the lid and the electric motor spins up the tires, and the internal brake stops it for you. Big difference doing small FWD car tires or 3/4 ton truck tires. That is much more work for the machine to do.

 

[R413]

Trying to get traction on the street is a tough thing anyway. More gains in different compound rubber than wider tires.

Always cracks me up when people who can't get away from the BFG radial TA are talking about better traction with a bigger tire, there is none to be had on those!

 

[33 IMP]

Keep your rims, buy better tires.
That said..... my street tire setup is 15x6 front steelies, 15x8 rear steelies, with 235 and 275 t/a radials. For traction, they are hopeless.
My track setup is 15x4 and 15x8 centerlines, with skinnies and slicks. The track setup is 100 lbs lighter than the street setup, and that you can feel.
Best I've run on the street t/a's is low 13s, will run low 11s on slicks.

 

[BSB67]

If you go to the track it will show up on the time slip, both et, and mph. I think it’s meaningful.

That said, if you only drive on the street, your butt meter will not know the difference.

 

[6PKRTSE]

From 235/60 on steelies to front runners on Weld Aluminum drag lites and same size on the rear for tires from steelies to the welds. Only a couple of hundredths differences in e.t. and maybe 1-2 mph. Could have even been weather temp change, but not a noticeable difference between the two even though it was like a 30+ lb difference.

 

[WileERobby]

Keep your rims, buy better tires.

^^ and that is all you need to do.

 

[toolmanmike]

Just wondering if anyone has done a study on this? I have 15x8 Stock(ish) steelie rallye rims at the rear now (center caps and trim rings and 275/60/15 Tires), but spin pretty easily, thinking about getting 15x10 rims with larger tires for better traction, however would that extra weight slow the car down?

Or would an aftermarket Aluminum rim be better if they are lighter weight? Perhaps, the difference is so miniscule it doesn't really matter? IDK? This is why I ask.

Any opinions on this?

Thanks!

In answer to your original question. Will larger rims slow down a car? Not that you'll ever notice.

 

[j-c-c-62]

First, I adhere to the concept in racing, "everything effects everything else"
First, there is total wheel/tire weight, not sure what difference that alone makes on acceleration, but unsprung, it matters,
What applies most here on acceleration and braking is rotational inertia, that is harder to calculate/measure, and it matters to some extent, and can be different for two wheels that weigh the exact same
Each opinion here will vary in response to your question I suspect.

 

[dvw]

I swapped my racecar to lighter wheels this year. The 4 together weighed 30lbs less. Made 120 passes this past Summer. No noticeable difference.
Doug

 

[BSB67]

I swapped my racecar to lighter wheels this year. The 4 together weighed 30lbs less. Made 120 passes this past Summer. No noticeable difference.
Doug

Same size tires?

 

[dvw]

Same size tires?

The only difference is the rear gear. 4.30 with heavy wheels, 4.10 with the light wheels. So isuppose there could be something the re. Every thing else is the same except the wheels. Best of 8.96 with the heavy wheels. 8.97 with the light wheels
Doug

 

[BSB67]

The only difference is the rear gear. 4.30 with heavy wheels, 4.10 with the light wheels. So isuppose there could be something the re. Every thing else is the same except the wheels. Best of 8.96 with the heavy wheels. 8.97 with the light wheels
Doug

Just curious. We've only changed/tested wheel and tire changes. Not one or the other. We gained a tenth. But the front tire went from a narrow bias ply to a considerably wider steel belt. I would guess that the location of the weight matters considerably, and the change is probably not linear relative to distance from the centerline.

 

[Justasgood]

Taller wheels increase rollout cutting your gear and your off the line speed. Lighter ( especially Rolling weight) is a good thing.

 

[Geoff 2]

It is not the static weight that makes any significant difference to performance.
It is the rotating weight, the MOI, Moment of Inertia.
You will see folks brag about how they went quicker after switching from a 13" converter to a 10" CV & claiming the improvement was due to 'stall speed'. Stall speed might well have played a part....but so would the reduction in rotating wt. The further out from the centre that the weight reduction is, the greater the improvement in acceleration.
D. Vizard did some drag strip testing on this: wheels & [ I think ] flywheels. ETs improved with lighter parts.

 

[dvw]

Here is the strange thing. We run index often. We are very accurate in doing so. Able to dial from mid 9.0x to 9.25 +/- .01 with 10lbs/.01 second of ballast adjusted for weather.
Doug

 

[BSB67]

I don’t think anyone is questioning the physics of accelerating a rotating mass. I think the question is: does it really matter? The answer to that question can only be decided by the OP. And he is getting feedback, hopefully it’s helping him.

Beyond just the mass, the power required to accelerate a 35 lb flywheel or converter to 6500 rpm 3 or 4 times in 11 seconds, verses a rim to 1500 rpm once in 11 seconds will be different, as an example.

Just in the past several months, I changed rims and tires on my car. It added 20 lbs total, but all in the rim. I made about 8 passes with the new rims/tires. I also made two other changes at the same time, so I cannot make any claim to the effect of the rims and tires.

Finally, I doubt many folks are controlling the controllable variables and accounting for the uncontrollable variables at the track as well as Doug. Although I absolutely trust the physics, I believe Doug’s results are accurate, and they speak directly to the OPs question.