Lighter wheels

Hai. I have steel wheels on my old RR; 15x7 on front and 15x8 on the back. If I switched to aluminum, I think I could get 8-9 lbs lighter each corner.

If you have ever switched to lighter wheels, without making any other changes such as tire size or gears, did you notice any difference on the butt dyno?

I don't do any racing; just drive around on the street, but if lighter wheels would make it quicker and stop better, I would try them. Thanks.

You wouldn't notice the change.

The new Ford Mustang Shelby GT350-R with the 5.0L flat plane crank has carbon fiber wheels. These are substantially lighter than even the non "R" aluminum versions.
The lighter wheels allowed the car to accelerate 1.1 seconds faster from 50-70 mph. This comes at a very steep price though. The front wheels are $3400 each, the rears are over 4 grand apiece!

If your car is otherwise a total slug, then dont bother. But if its dialed in, then light rims/rollers improve EVERYTHING.

Okay. A 383 RR is not considered a fast car these days, but it's still quick enough to irritate people in modern cars.

I was thinking the way to get more out of it everywhere was either lose weight or more cubes, and more cubes is expensive. If you start playing around with cams and intake and all that, always a trade-off.

I would think 8-9lbs per wheel in rotating weight would be noticeable, and especially on the CF angle. I always wondered why city buses don't have Alum wheels (6?), since they start and stop nearly every block, for their entire life cycle and alum wheels them saves 40+? lbs per wheel, but fire trucks have them and they maybe move twice a day?

Maybe the steel wheel is more durable in that situation, going around all day on bad streets on a bus full of people. If it fails, it would probably bend but not break.

The formula is 100lbs= .10 in the 1/4 mile with a performance set up. Think you will notice that on a street car? You are only talking 32-36 lbs.

I agree but rotating weight might have greater effect.

It's works the same no matter where the weight comes from.

Do it for improved looks if nothing else, weight is a bonus.

Incorrect. Rotating weight has a greater effect. And the farther the weight from the axis, the greater the effect.

Look at the gain per dollar. Wheels and probably new tires @ $200. per corner minimum. For that same $800. you can get that sucker moving a lot quicker than new wheels and tires would.

Seems real interesting most race teams try to remove body and chassis weight rather than lighter wheels and tires. If I was going to spend a pocket full of cash to make my street car faster it wouldn't be spent on wheels and tires which wouldn't produce near as much performance as some engine or trans upgrades for the same bucks.

Shaving tires is an unseen performance advantage and with a significant cost downside , but where weight counts the most, besides it other benefits.

I agree that a swap to lighter wheels is probably not the best "bang for the buck", but the fact remains that reducing rotating weight has a greater effect than reducing an equal amount of fixed weight. And last time I looked, almost every race team used lighter wheels than stock.

Rotating weight is different and will make a bigger difference.

Please explain how it makes a bigger difference.

Every race team uses lighter chassis, bodies and interiors also.

I think you guys are confusing "rotating weight" with "unsprung weight". And generally, when teams take weight out of the car its usually because they've already reduced the unsprung weight as much as possible. And further to that point, weight is often shifted as opposed to removed - to change the center of gravity, etc..

So to the point of "rotating weight", this is more commonly referred to as "inertia" and would apply more to flywheels than to wheels and tires.



Hmmm ... I'll bet you a Nascar wheel weighs more than a stock wheel!


Anyway, the point isn't whether there is something to be gained from lighter wheels, the point is that there are greater gains to be made spending the same money elsewhere. For the price of a set of wheels and tires he could do a cam, intake and carb and possibly more if he bought good used and does the work himself.

It's unsprung weight the hardest to lose and the most benificial. The car should stop accelerate and handle better, what that looks like on a spreadsheet is individual to the particular car. I'm unaware of a formula to calculate what gains to expect but with your car as a baseline back to back test will net you the results. Can your backside tell? I have no idea. But 36lbs of unsprung is significant

The guy want new wheels, so let him get new wheels. He is not building a race car. Yes it makes a difference in performance.

A magazine did a test on this in the 80's, a 15 second small block streetcar picked up .25 and 3 mph in 1/4 mile on the time slip going from 15" rallies to weld wheel draglites. Same tires and traction.

Its unsprung AND rotating weight... win and win. Thats weight at the very end ov the powertrain that your engine has to spin. A heavier axle costs performance, a heavier driveshaft costs performance, you dont think 8 extra pounds a wheel... spinning at a far greater diameter (thus speed), demanding far greater torsional strength is not going to cost performance? And a reason why so many teams dont go nuts on re-sciencing the rollers is because its largely been done already. Light wheels and tires are readily available, and more reasonable in price than years back. To get beyond what you see out there requires an investment far beyond return. Also, some stock car stuff is as light as its allowed to be, or as light as it CAN be. Far more stress on that NASCAR wheel than a local roundy-round wheel, or the street. You can buy 19lb circle track wheels, but the actual NASCAR ones are far heavier i believe.

If strength did not matter, we'd all be running those ugly ol' Weld Drag Stars...

fire trucks have aluminum wheels because firemen like them shiny [not that there is anything wrong with that]. city buses have steel wheels because they run into, and over, all kinds of stuff that would trash aluminum wheels in quick order. plus, i believe steel wheels are cheaper than aluminum and don't require constant polishing that will save the city big bucks in their yearly budget. garbage trucks are steel wheels for the same reason and i would hazard to guess they start and stop way more frequently than city buses.

Fire trucks have aluminum wheels because the departments have ridiculous budgets that they have to spend.

and that too, although it seems the departments out in the sticks are always having fund raisers. but if i had need of their services, i don't think the budget money would be my first concern.

1. Any CDL driver that has any record of running over stuff on any regular basis would promptly be dismissed/transferred, and if indeed that was the case, a $400? tire plus labor would be the first casualty, and I don't think the record would support that thesis.
2. Class 8 OTR and others have a long history with billions? of miles and alum wheels have no greater known failure rate then steel ( they are forged 2024 aircraft alum).
3. Alum wheels don't require any polishing, don't require any rust protection, and are fine with only the normal wash cycle maintenance.
4. The taxpayer who subsidizes the city buses on their fuel guzzling, every block starting and stopping, would be very rewarded in the 200?lb rotating weight reduction, both in fuel and brake tire wear costs on each vehicle, if the city buses swapped their steel wheels with the over budgeted first responder fire departments, and let the fire depart when not fighting fires, visit the bus depot and polish their new alum wheels.


Edit, went to check my sources, looks like Alcoa, a leader in alum truck wheels has changed over Aircraft 2024 to 6061 forged wheels, likely for cost and better corrosion resistance, not sure it matters much, as the track record is still solid.

In theory, yes. However I have yet to hear real-world results from one person who claimed to see gains in the 1/4 mile that were anything more than the result of losing the equivalent amount of weight from anywhere else in the car.

it's kinda obvious you haven't watched too many buses in cities like pittsburgh with the narrow, twisty streets, and have not been to the land fill and watch garbage trucks in action. and i'm certainly not debating your other points which are valid in every aspect. just stating what i have personally observed over the many years i have been on this planet. and it is really no comparison to argue paid fire companies vs volunteer fire companies, which i have first hand knowledge. carry on.

No I have long term daily experience seeing what you mentioned, my main point on wheel abuse, you would see and pay for tire repairs/replacement way before, and in much higher frequency then you would wheel damage driving caused abuse. The tires would be the Canary in the coal mine.

It's funny to hear the debate that it doesn't matter.

1) Put a 10lb weight belt around your waist and go for a run.
2) Add 2.5lbs to each wrist and both ankles.

Now which case do you think you'd be able to run faster?

i really didn't think i stated that it didn't matter. just "sometimes", for what ever reason, "somebody" decides that steel wheels are better to use than aluminum. take the post office for example. [please?] how many aluminum wheels you see on mail jeeps ? none here. fedX and UPS. all steel here at this hub and that includes the OTR rigs. no need to waste time and materials [paint and stripes on the outer rim edges] on alloy wheels, plus the savings on fuel. police and sheriff vehicles ? none around here, including the state police. lots of miles and fuel used, could use the extra money someplace else for sure. and as others have said, the time slips and "butt meters" show the same results with either in some instances. i'm not disputing or arguing for or against either. just observations. and to think i am accusing city bus drivers of running over everything and anybody is ludicrous. just not too many open man holes, tall curbs, street drains, curbs with street drains, etc. on the open roads. tires are certainly the "canary in the coal mine". and i can't run any more, plus i walk with a cane, so i'm not gonna put weights on and do a marathon.

sorry if i ruffled any feathers. that was not my intent.

You couldn't be more wrong.

Rotating weight is literally a flywheel. It has to be accelerated and decelerated in order for the car to perform.
Totally different than static weight.

Race teams may be ruled constrained in what wheel composition they may or may not use.

Really?

The 4" skinnies they run for front tires ring a bell?

Back tires are optimized for traction, maybe at the expense of possible weight savings.

Of course your examples are straight line guys anyway, the only handling they care about is making the turn back to pit row. Anyone interested in handling and considering new rims would be smart to look at weights as well.

Weights on the wrists and ankles examples should end this.

Anyone ever run a spin tire balancer and see how hard it works to start and stop a heavy wheel/tire? Even larger diameter alone will change this, it is further out from center, more centrifical force.

I hope the underlying point I was trying to make, wheel inertia matters little with constant speed, but anything that starts, and stops, especially frequently, consumes power accelerating (fuel/hp) and has to give the stored energy back up under braking (heat/brakes/tires). Thinking any municipalities can see the benefits of large Alum maintenance free wheels on high use vehicles, is obviously never going to happen in my lifetime, unless looking "shiney" becomes the in thing outside the fire dept. Our understanding of why is likely where we most differ.

[ Moparts Family Site - Keep it Friendly ] does garbage and fire trucks have to do with this? So many outside variables.

The answer is lighter wheels have such a minor gain that most gains will go unnoticed but here is a fact, they will not hamper the performance. It brake better, turn better and for sure accelerate better.

I like the ankle weight example and here is another one for those who are not convinced. Jack your rear wheels off the ground. Remove the rear wheels and drums. Punch the throttle in neutral, punch it in gear and repeat with the drums and wheels on. The throttle response should be a great lesson for you.

Maybe to help those with limited imagination envision a problem and/or a like solution?

Care to share some of those "outside variables" that negate the correlation, if you can?

Find lighter brake rotors, I am looking at the carbon fiber rotors, I can cut the weight in half on a rotor. Match this a lighter wheel and it might make a difference. Tim

Yes.

I took my heavy stock steel wheels off and put Weld Draglites on. The Welds were so light you could flip them around with one hand like they were cardboard.

And, to answer your question, in my case it did not make a lick of difference in day to day use.

Damn. Maybe some ov us are just more sensitive than others... I went from 15x7" (28lbs) cop rims to 15x7" Weld Drag Stars (13lbs). Tires might have been +/- 1-2lbs, not much, dont even remember which way. The difference was drastic. So much so i drove on those Welds... against the advice ov many friends... until i bent two ov them. That was just in daily driving (hard driving... but no curbs or bumps). LIGHT rims... but flimsy as hell. Gonna go with 19lb 8"'s on my Challenger instead ov the 26lb 8" steelies and caps, and yeah, i expect it to make a noticeable difference.

Another interesting anecdote... We swapped rollers on the girlfriend's 96GT from the stock 46lb 8" rims and 245's to cheapo (read solid, but HEAVY) E-bay 18x10's and 275/295's. They were 57/59lbs. The car slowed noticeably. Yes, the added width was worth a bit there i'm sure, but not all. The strangest thing was, that even now we had a nice open wheel... with LOTS ov airflow... we could not keep rotors on that car. In 4 years we went through 3 sets ov rotors... and the second set were 'the best' you can buy at the local shop. All that added grip really laid a taxin' on them poor little rotors. Did not expect that. My own 96GT (same stock rollers) never even got a brake job in the 3 years and 30K i owned it, and that was with much harder driving.

This makes zero sense.

Some of you need a critical thinking class..

Yes its good to bring examples and illustrations but we do not use deliver trucks as a template for making our cars perform better.

Aluminum wheels on trucks may be there because the customer wants them, they are lighter, they look better or their budget says so. Trying to sound positive and I hope you recieve it this way.

I will, but physics apply no matter what the end vehicle, plane, truck, car, lighter is better, etc, on this topic, no matter what the personal desires of the users or how they apply those desires.

IMO this topic might also benefit from some discussion on how to measure a driveshaft angle and maybe which engine oil is the best to use as well...

It makes perfect sense. So off you go.

Think I will try some sloot mags and see what happens.

Yes, inertia is your enemy and you are proving the point: Tires and wheels are exactly like extra flywheels at each corner of the car - They are mass the engine has to keep accelerating throughout the whole run. Less mass is a faster car.

- Art

I agree, as I stated earlier they are four flywheels. And not only does our vehicle have to accelerate them, it has to decelerate them too.
And they located at the four corners, much worse than the actual "flywheel" which is extremely idealy located!

Light wheels are a huge issue. The autocrossers know this!

A gyroscope would be a better analogy for wheels and tires. A gyroscope will resist ANY change in direction, that also includes acceleration in both the positive and negative direction.

Less weigh means less gyroscopic effect

https://woodgears.ca/physics/gyro.html

Uhh, still no.

Some of them can be quite heavy actually..

If you want to save weight, a forged aluminum wheel is going to be lighter than a cast one (especially an older slot mag that only has smallish windows with no material)

Just weigh them. Most ov those old-school slots were way light. I remember 18 and 19lb 15x8" rims. The old bias-ply 'performance' tires were lighter than radials too. Could make for a fairly aggressive weight loss where it counts. Almost worth using...

All those old CAST aluminum rims were (in general) light. Now... i wont say they were strong... but they were light. You know how the saying goes...

Modern forged is obviously badass. But damn... man, expensive.

Okay, here is some unscientific data using my bathroom scale.

On the front, I went from Cragar Soft 8, 15x7, with 235/60/15 Futura GLS to the Summit 531 alloy, in 15x7 with the same 235/60/15 tire.

Cragar Soft 8, 15x7, with 235/60/15 Futura GLS weighed about 51 lbs.

Summit alloy, 15x7, with 235/60/15 Futura GLS weighs about 43 lbs.

Some other measurements with the bathroom scale:

Chrysler 15x7 police with 235/60/15 Futura GLS weighs about 50 lbs.
Chrysler 15x7 police with 215/65/15 Cornell 1000 weighs about 45 lbs.
Chrysler factory 15x7 steel with 235/60/15 Goodyear Eagle ST weighs about 45 lbs.

Don't take any of that as gospel, because those measurements were made on an analog bathroom scale.

Butt dyno test will probably be overnight sometime. If it works out, I will switch the 15x8 steelies in the back with alloy wheels.

I'm not going to lie, but I kind of find this thread a little funny.

Yes, going to a lighter wheel should technically make your car faster. How much? It depends on what you have on there now vs what you plan on putting on. By decreasing weight, you're decreasing the amount of inertia required to rotate the wheel (i.e. less power to rotate). But in another sense you can also think of it as an aid to steering as now you have less mass to rotate side-to-side.

If you want to have a fun math exercise and a very rough ballpark as to how much less energy is required to spin your wheel, treat the wheel and tires as cylinders. For the wheel, the energy needed to rotate it is Iz = (m*r^2)/2. Where m is the mass of the wheel and r is the radius. For the tire, Iz = (m/2)*(R^2+r^2). m is the mass of the tire, R is the overall diameter of the tire, and r is the inner diameter of the tire (or just use the diameter of the wheel). Add the two together and you'll see the total energy. Do it for both setups and take [(IzOld/IzNew) - 1]*100% to find out how much more energy your old setup takes to spin than your new setup.

Wiki for equations: https://en.wikipedia.org/wiki/List_of_moments_of_inertia

If you look at the formula, you're going to notice that a change in radius of the wheel or tire is going to have a larger effect than changing the weight of the wheel. The radius is an exponential. Also, if you think about it, a tire weighs about about the same (+/- 15% depending on wheel and tire setup) of what the wheel weighs. So, technically going to a smaller or lighter tire will likely have more of an effect than a lighter wheel since all of the mass of a tire is outside the perimeter of the wheel (i.e. farther from the center of rotation). Most people have the problem; however, with traction going to a smaller tire. As mentioned before, the rears of a drag car are fat and meaty to get as much traction as possible (notice that a lot of people use lightweight wheels though), but on the fronts, they use pie cutters as they're easier to rotate about its axis.

Recent article testing / discussing effects of lighter wheels:

http://blog.caranddriver.com/tested-quan...n-fiber-wheels/

If nothing else, the lighter wheels make it a little easier for me take them off and on and move them around. I didn't care about that 25 years ago but I am starting to now.

Those tests of aluminum versus carbon fiber wheels are interesting, particularly the coast down.

In the Bosch Automotive handbook they give the equations for finding tire rolling resistance and aerodynamic Cd by coasting down from 60 mph.

Others have written that it is better to find these two values by coasting down two different grade hills at "terminal velocity"
because this is a steady speed test,
And rotating mass like wheels, driveshafts, gears, etc,
cannot add or subtract flywheel rotational energy
to skew the measurements.

The Car&Driver tests show that 20 lbs of wheel weight can indeed be measured by common stopwatch or ruler.

Anyone that has spent time in their car at the drag strip will know how much of a difference the wheel/tire weight makes.

True.

I've got a similar set of equations and spreadsheets. Stuff varying from how much horsepower it takes to drive a vehicle at X speed, Y grade, and Z size. I've also got the set of equations for a similar test that you measured by doing a coast down test.

Real world test. http://www.hotrod.com/cars/project-vehicles/116-9905-light-vs-heavy-wheels-comparison/

"I've also got the set of equations for a similar test that you measured by doing a coast down test."

The thinking being a longer coast down result is from a wheel that stores more energy, correct?

Wonder if in that test, wheel "fan" energy is a factor when 4 alike wheels are used?