Volk Racing

Topic that many people debate on, and just want to make it straight.

When talking about wheel weights and size, size is more signifciant than weights of the wheel, and that's including inertia.

For example purposes only, lets compare two wheels/tires sizes:
Stock GS wheels: 225/50/16 = 631.40mm overall diameter.
20" Wheels: 225/40/20 = 688.00 mm overall diameter.

Let's say the GS wheels/tires is about 40lbs.
And let's say the 20" wheelstires is super super super light @ 2lbs. (extreme for simplicity of understanding).


Alright, if you lift the car off the ground, and have the wheels spinning freely, you can spin the 20" rims up fast because of lightness of inertia. The GS wheels would spin up slower because of inertia weight is more great.

BUT when the wheels are on the ground trying to pull the car's weight, inertia becomes so small that it's insignificant compared to the work it has to do. Even though the inertia weight of the 20" wheels is much more less than the GS wheels in my example, the GS wheels will out accelerate the 20". Why? Because diameter = torque. It takes the engine MUCH MUCH more work to get the car to accelerate when having larger diameter wheel/tire because the car has less torque now to move the 3500 lbs car. The GS wheels/tires will accelerate much much faster because the diameter is small, thus having much more torque to push the car in acceleration.

Because it's all about torque to accelerate the car, inertia of the wheels is to small compared to it that it's insignificant.

The only way wheel weight is good for is when you are using the SAME exact size wheel, that's where you have equilibrium torque, so now it's about inertia. Another thing wheel weight is good for is when the wheels are spinning fast already, it just makes it lighter on the steering wheel (inertia factor), like a gyroscope.

This is only for (acceleration), top end speed is different matter, and subject wholey that doesn't relate to weight at all.

Conclusion... for acceleration, size is more significant than weight, Torque is more significant than inertia.

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1994 GS (18 X 8.0, 18 X 9.0)

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johndftc

interesting point you bring up, i've never really thougth that much about it. IF you really wanted to do a hardcore analysis of the differences between the different size wheels, you could find the polar moment of inertia of each wheel, (i think) or the radius of gyration (the radius at which all the mass in the wheel appears to be located at) and figure out exactly how much power the engine puts in to accelerate the wheels (angular and linear acceleration). its been a while since i took engineering dynamics lol

Volk Racing

Haha, yea. It's been a while for me too, but I was trying to make this simple as possible so the ones that don't understand physics or engineering understandings can feeding wrong to the world.

Also, another factor that needs to be put in for hardcoreness is the amount of acceleration which is the power of the tranny multiplied by the wheel size.

Example is my current rims/tires are ONLY 6mm taller in diameter than stock, but tires and wheels are much lighter. But that small difference in diameter makes a difference. Acceleration in the low RPM torque power band has decreased greatly from stock wheels, but once it goes closer and over the max power band, the acceleration is much faster than stock wheels, when it actually has also decreased at the tranny. Its because of max power VS my smaller increased diamter wheel, around the max power band, 6mm differnce because less significant, and the larger diameter allowed it to go faster. Alot of depth explaining in that, but some will get the point.

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1994 GS (18 X 8.0, 18 X 9.0)

B===D~(|)

johndftc

with larger size wheels you have a higher top speed too, in theory at least

B+O

interesting, but the 225 20" tire would be a 35 series, anyways, though. i agree with you on this whoel thing. the rolling circumference of the wheel and tire make more difference than real weight. that's why i say all thos epoelle thinkin gthat 20s are stupid because they loose speed and are heavy are greatly missinformed...

for BEST performance 18s aren't ideal either. 16-17 on the Legend is optimal for the best performance, and 16 is really the best. on smaller cars a 13-15" tire and wheel combo is the smartest thing.

18-20 are JUST FOR SHOW, and are SUBJECT TO TASTE

thank you for putting some weight (no pun intended) behind what i have been ranting and raving about.

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takemorepills

You guys are way out there. These things matter on a Civic hatch with a turbo B18C, but it really doesn't apply to a car that is soooo hopelessly heavy to begin with. Jezzis, for f**ks sake give it up already

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LegendFan91

Yeah the car is heavy to begin with, but unsprung weight is a whole different story.

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Volk Racing

Well, it's just for subject matter.
There are some folks that believe it's all about inertia, but they don't take into account the weight of the car that it has to pull.

BnO, Yea, I chose 225/40/20 just for a larger overall diameter for example sake.

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1994 GS (18 X 8.0, 18 X 9.0)

B===D~(|)

johndftc

woah calm down there, its just good convo... and unless the inertia of the car Is 100 times greater than the inertia of the wheels and their rolling, then you can't really exclude it so quickly. Have you ever tried to spin something heavy by hand and get it going fast? with 4 wheels at once it actually does factor in to car's acceleration

Legendary9deuce

WEll, I for one am happy that you posted the thread. I found it informative (i'm not trying to be funny I really mean it...) What this tells me is that If I do end up getting the 19's that I want I have to keep my stock rims. Or ateast 2 of em, if I decide to go to the track. Thank you guys.. Thanks VOLK..
;0

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Tinkindling

Great post! This sort of discussion helps us all understand our cars, and how the mods we choose will affect the car's performance as well as it's looks.

Obviously, in a perfect world we want a tire/wheel combo that looks good, is extremely light, and has a small effective radius when we accelerate, and a large radius for when we are just sitting there looking at the car. Sound impossible??

Light weight (low unsprung weight) is great for handling and ride, and helps the shocks do their job.

And for those who think that the moment of inertial of the wheels is insignificant forget something that automotive engineers all know: "If you want to reduce the weight of a car by 100 pounds, you find 1600 places where you can make a part lighter by one ounce."

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Tinkindling

Great post! This sort of discussion helps us all understand our cars, and how the mods we choose will affect the car's performance as well as it's looks.

Obviously, in a perfect world we want a tire/wheel combo that looks good, is extremely light, and has a small effective radius when we accelerate, and a large radius for when we are just sitting there looking at the car. Sound impossible??

Light weight (low unsprung weight) is great for handling and ride, and helps the shocks do their job.

And for those who think that the moment of inertial of the wheels is insignificant forget something that automotive engineers all know: "If you want to reduce the weight of a car by 100 pounds, you find 1600 places where you can make a part lighter by one ounce."

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Stock except
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Phatty LS

I have seen .2 second gains in the 1320 by dropping wheel weight (same size) by a mere 5lbs.... (23-18)

Just a thought

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Volk Racing

Yes, you are correct! That's because it's the SAME overall diameter between the two different weighted wheels. That's when weight becomes significant. But the point of this thread is DIFFERENT sized overall diameter makes weight become insignificant.

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1994 GS (18 X 8.0, 18 X 9.0)

B===D~(|)

Tinkindling

The diameter, or rolling radius of the wheel can really affect performance. Before I changed to GS rims and 215-55 16s, I could beat Hotstartups car. I checked the tire size calculator on the net, and found that the 215-55s are too big around. It's the same as if I had changed my diff gears to a 5 percent higher gear.

When I get back to the correct rolling radius (225/50-16s) my car will have it's old acceleration back, and Zah better watch out!

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