Performance Wheel Test - A Look at Wheel Weight, Density, and Stiffness

[mike_ekim1024]

https://www.motortrend.com/how-to/mo...nce-wheel-test

It’s true, wheel weight by itself doesn’t give you much info. Where is the weight? A lighter wheel with less mass in the middle isn’t going to do much for you, if I understand. And then you have the tires, which are 20 lbs by themselves, and at the edge of the rotating mass. Sure 20 lbs vs 30, 20 will likely be better, but a lot 2 lbs difference?

[Breadman]

On average people are too dumb to understand what rotational inertia is, that is why just weight (technically it should list mass instead) is listed. I=mr^2 so for a given mass as the distance from the axis of rotation increases the resistance to rotation will go up exponentially. The tire is ignored because it is assumed the same on every wheel.

[mike_ekim1024]

Originally Posted by Breadman

On average people are too dumb to understand what rotational inertia is, that is why just weight (technically it should list mass instead) is listed. I=mr^2 so for a given mass as the distance from the axis of rotation increases the resistance to rotation will go up exponentially. The tire is ignored because it is assumed the same on every wheel.

But there are a few pounds difference between Michelin and Bridgestone performance tires for example. Shouldn't we be looking at that?

[Breadman]

Originally Posted by mike_ekim1024

But there are a few pounds difference between Michelin and Bridgestone performance tires for example. Shouldn't we be looking at that?

You don't really want to be testing things with multiple independent variables

[mike_ekim1024]

Originally Posted by Breadman

You don't really want to be testing things with multiple independent variables

Oh, yes, I don't mean test the wheel and the tire at the same time. I mean once you stick with a wheel, to test the tire independently. The point I was making was that the tire is just as heavy as the rim, and it's on the very edge of the wheel.

[terboboost]

Rotational inertia is not the primary reason for lighter weight wheel/tire...the primary benefit is less unsprung weight. Less unsprung weight allows the suspension to work more efficiently and effectively.

But as this article attempts to show, but does a poor job at, is that wheel weight really doesn't matter for 99.9% of applications. You aren't going to feel it in unsprung mass, and you certainly aren't going to feel it in inertial effects. This does not hold true if you start comparing extremes. A 20 lbs monoblock compared to a 35lb 3piece wheel will be noticeable...but I'd bet at least 50% of this forum still couldn't tell the difference! These 1, 2 lbs weight differences only matter if you are in the upper echelon of racing.

What does actually matter, and what many people can feel, is what this test and most others seem to disregard. Wheel rigidity and impact strength. Wheels bend and twist quite a bit, especially on track, and this can be felt through the steering wheel. Lower quality wheels, tend to have less overall strength, impact, tensile, and compressive, AND they tend to be less plastic in deformation...aka you're wheel will crack catastrophically instead of bend. And to make matters more complex, material properties are only half the equation, the other half is design characteristics, and the devil is in the details there.

Wait until most of you figure out the term "forged" or "made in china" doesn't mean a god damn thing to the wheel's quality, and can even indicate the opposite of what you might think.

[Spuds]

I can tell the difference in inertia when I put on my summer wheels and tires vs the "winter" (all seasons on stock wheels) set. I think the wheels are -5lb and tires are -2lb. I did calculate it out once* and the tires made more of a difference mathematically.

*Approximating the wheel as a simple cylinder and tire as a simple ring.

[lapsio]

Originally Posted by mike_ekim1024

Oh, yes, I don't mean test the wheel and the tire at the same time. I mean once you stick with a wheel, to test the tire independently. The point I was making was that the tire is just as heavy as the rim, and it's on the very edge of the wheel.

But they DO list weight of motorsport tires quite often. Not necessarily in all sizes since well there's A LOT of tire sizes comparing to rim sizes, but still you sometimes can find info about tire weight.

For example here you can find tires weight in specs at the bottom:
https://www.tyrereviews.com/Article/...-Tyre-Test.htm

Retreaded semi slicks are also often described as heavier comparing to regular tires so yeah - it is something that people consider when buying tires. Especially competition ones.

That said I believe weight in case of tires is much more complicated because it's directly connected to properties like sidewall stiffness for example. I think rims have less variables and when you're looking for performance then basically you mostly care about size and weight. With tires there's billion of variables and weight while is there it's probably secondary parameter comparing to what most people look after - compound, driving characteristics, feedback, operating temps, wet performance etc etc

[foshjowler]

The biggest difference I notice in weights between my different wheels is how easy they are to take on and off. When you're swapping wheels 2+ times a month it becomes very noticeable. As far as driving goes, eh I've never noticed a massive difference between wheels. I'm sure it shows up a little on the stop watch, but the biggest differences are going to be with tire compound.

[vindiesel]

I just drive around with 2 gallons of gas in the gas tank. I unsprung 60lbs of liquid weight compared to full tank. Didn’t have to buy light weight wheels or gut the interior. So much cheaper.