Wheel STIFFNESS matters! -We test Carbon Revolution's Carbon Fiber GT350R wheels vs AL wheels.

[BillyJRacing]

Carbon, like most other materials, has wide variances in strength and stiffness based upon a huge number of highly variable factors.
I'm just very uncomfortable with the assertion that "carbon is better" and "Carbon is stiffer" as unsupported glittering generalities.
I am absolutely certain that I can design and manufacture a forged aluminum wheel with 100% of any carbon wheels "stiffness " within 10% of its overall mass at one third of the manufacturing cost.
That reason is why carbon has made very little inroads into a share of the wheel market.

Carbon is lighter, yes. It has fantastic tensile strength, yes. But wheels have certain minimum thickness requirements that limit the advantages of carbon.

You have to tell the whole story.

Carbon does have a extremely wide variance in terms of weight, strength, and stiffness. It can also have stiffness engineered into an object in ways that are impossible with traditional metals -all mentioned in the article. Your responses suggest you have not read the entire article. If not, I urge you to.

It's impossible to make a forged aluminum wheel to have 100% of Carbon Revolution's wheels stiffness with only 10% more mass. Now i'm sure you can make a cheap, poorly engineered and manufactured carbon wheel that is super flexible and has the same stiffness of your proposed wheel, but you can't match the weight and stiffness of Carbon Revolution's wheel -it's impossible from a material science standpoint.

If you could defy material science, I know a few guys at NASA and the Military that would like to talk to you.

The reason carbon has made very little inroads into the market of wheels is mentioned in the article. CR is the first company to put them on a mass-production OEM. They are also expanding their production 15X (from 10K to 150K a year). You'll see them on more and more cars in the next 5 years.

I have some sympathy for @Forgedwheeler though - his point is that while aluminum isn't as strong or as stiff as CF, you can still make a stiff wheel out of it. The stiffness of the finished wheel is determined by the design, not just the material.

The classic racing wheel design with five or seven y-shaped spokes (presumably) produces adequate stiffness in rotation to handle accel/decal forces while providing the best stiffness laterally for lateral g's. Making a wheel out of CF has to be more complicated because the stiffness may well be different in different directions depending how the fiber layers were built up.

Of course, the easiest answer is to build wheels out of the stiffest, strongest material you can find - steel is 6x stiffer and 4x stronger than aluminum but it's only 3x as heavy. Theoretically, an optimized steel wheel could be lighter than an aluminum one.

Absolutely. There's a reason the 5-7 "Y" spoke design is used - because that is the general optimal design for strength and stiffness. However, from a material standpoint, the only way an aluminum wheel can match carbon's stiffness is by being SIGNIFICANTLY heavier.

As mentioned above and in the article, the carbon fibers can be layed in directions to increase the strength in load paths that cannot be matched by aluminum. Then add geometric shapes (hollow spokes) and carbon further stands apart in terms of strength, leaving aluminum behind.

Theoretically, given the same weight, an optimized steel wheel would be barely stiffer than an aluminum wheel but would not have the same strength. Look at the material properties on Page 6.

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[NDALLAS40]

Hey guys,

Do you own a GT350R with Carbon Revolution's Carbon Fiber wheels, or are you looking to buy new wheels for your GT350, Mustang, or any car for that matter?

After a year in the making, setting up this test, conducting the best back-to-back test of Carbon Fiber wheels vs. Aluminum to date, and writing the article, my review and comparison test is now ready.

This article will hopefully teach the importance STIFFNESS plays in ALL wheels, and the effects of reduced unsprung weight, rotational inertia, NVH, strength (which is different from stiffness) has on ALL wheels. You'll also learn that carbon fiber wheels are a game-changer, forged & cast wheels have the same stiffness, and that lighter is not always better when choosing a set of wheels.

Hopefully this article will provide you with more knowledge to make better wheel purchases in the future.

https://motoiq.com/tested-carbon-revolution-carbon-fiber-wheels/

Enjoy!

-Billy

Motor Trend did an in-depth wheel comparison 4 years ago when the GT350's were first released. It was very enlightening. I have a whole new perspective on unsprung weight in motion. The wheels on the 350R are the single best feature of the entire build.

 

[JAJ]

Motor Trend did an in-depth wheel comparison 4 years ago when the GT350's were first released. It was very enlightening. I have a whole new perspective on unsprung weight in motion. The wheels on the 350R are the single best feature of the entire build.

I'd love to try a set of the CF rims with my CCB front brakes. The carbon ceramic brake rotors take 16 pounds off each front rotating assembly. Taking another 12 pounds off and increasing stiffness would be a very interesting (but expensive) exercise.

 

[BillyJRacing]

Motor Trend did an in-depth wheel comparison 4 years ago when the GT350's were first released. It was very enlightening. I have a whole new perspective on unsprung weight in motion. The wheels on the 350R are the single best feature of the entire build.

Here's their article:

https://www.motortrend.com/news/carbon-revolution-rethinking-wheel-aussie-style/

Another article:

https://www.motortrend.com/news/ford-spills-details-on-shelby-gt350r-mustangs-carbon-fiber-wheels/

Here is their comparison: (mostly dyno and acceleration):

https://www.motortrend.com/news/doe...ake-more-power-than-the-regular-gt350-wvideo/


If you read though my article, I'd love to hear some feedback. I was trying to focus more on the technical side of things, as well as general concepts and the importance all of those concepts from strength to stiffness and camber compliance plays on steering feel, peak grip, and transient response (that applies to ALL wheels, not just carbon). My track test, lap times, and tire wear all focus on the importance stiffness plays:

https://www.motortrend.com/news/ford-spills-details-on-shelby-gt350r-mustangs-carbon-fiber-wheels/

 

[Forgedwheeler]

A successful carbon wheel aftermarket program will be very unlikely. It currently costs in the range of $6000 to make a set of carbon wheels. That's one style and one fitment.
If you factor in the amortized tooling costs for several styles and a wide variety of sizes and mix in a generous helping of distribution profit margins, and you will quickly be in the $12,000-$15,000 per set price range. There is a very tiny market worldwide for wheels in that price range, dominated by a very few wheel companies with powerful brands and spectacular styling acumen.
Finally is the issue of style. Most carbon designs are just boring or worse, due to a variety of factors. There is an even tinier segment of hard core track guys who don't care about style.
Unless this changes, I would forecast the total aftermarket demand for carbon wheels to be no more than a few hundred sets worldwide.
There will be a few expensive OEM models with carbon, but the aftermarket will be extremely unprofitable to pursue.

 

[Zitrosounds]

I'd love to try a set of the CF rims with my CCB front brakes. The carbon ceramic brake rotors take 16 pounds off each front rotating assembly. Taking another 12 pounds off and increasing stiffness would be a very interesting (but expensive) exercise.

Your brakes reduce weight but do little in terms of handling dynamics. The wheels is where its at due do its diameter, weight and material. The #1 reason I bought an R is because of the wheels. I almost dropped 7k+ on wheels for my track pack and instead put the money towards my R. I would have never spent the coin on CF wheels alone but what a difference. I bought (now sold) a set of 350 wheels and tires and tried a buddy's 6G wheel. Drove each for a week and the difference was tremendous. I new right away I would not drive or track the R with anything other than the CF wheels. More so than weight, the feed back and response due to the material was beyond compare. Everyone that has driven my R, From Corvette, 911 to R10 owners comment on the R's steering. It's the wheels man!

Id let you try my wheels if you weren't so far away ; )

 

[oldbmwfan]

From a test perspective, the only thing missing IMO is the contribution of the wheel weight difference. Two ways to control for that:
1) Use CF and alloy wheels that are the same weight
2) Do a third test run using alloy wheels that are heavier than the stock Porsche wheels by the same amount that the Porsche alloys are heavier than the CR wheels

Doing it the 2nd way would give a sense of how much time 3 lbs per corner is worth, all other things being equal (assuming the heavier alloy was similar in design to the Porsche alloy).

Oh, thought of a third way: add weight to a CF wheel so it mimics the Porsche alloy. This could even be done in a way that neutralizes the difference in rotational inertia (by being careful about where the weight is added). Comparing two CF wheels where one is weighted like the alloy would truly isolate the effect of the stiffness inherent in the material and design. Would be pretty hard to apply that weight in a balanced way and have it stay on during the test, though!

 

[Zitrosounds]

A successful carbon wheel aftermarket program will be very unlikely. It currently costs in the range of $6000 to make a set of carbon wheels. That's one style and one fitment.
If you factor in the amortized tooling costs for several styles and a wide variety of sizes and mix in a generous helping of distribution profit margins, and you will quickly be in the $12,000-$15,000 per set price range. There is a very tiny market worldwide for wheels in that price range, dominated by a very few wheel companies with powerful brands and spectacular styling acumen.
Finally is the issue of style. Most carbon designs are just boring or worse, due to a variety of factors. There is an even tinier segment of hard core track guys who don't care about style.
Unless this changes, I would forecast the total aftermarket demand for carbon wheels to be no more than a few hundred sets worldwide.
There will be a few expensive OEM models with carbon, but the aftermarket will be extremely unprofitable to pursue.

What is up with theses absolutes!!! Dude!!! CF was unubtanium not long ago and now they are on a mustang for pete's sake LOL. I would say the CR carbon wheel program is already a success.

 

[oldbmwfan]

The #1 reason I bought an R is because of the wheels. ... I new right away I would not drive or track the R with anything other than the CF wheels.

Id let you try my wheels if you weren't so far away ; )

This. The only problem is I need two sets, and my pocketbook doesn't like that, so I have a set of forged wheels for the street. It rains too much where I live to run on only the Cup tires. I wish Ford had offered a 2nd set of CF wheels as an option for some discounted price at the time of purchase. I'd have paid an extra $8-10k for a spare set.

 

[Mountain376]

Thanks, Billy. Great article!

Too bad the temp data wasn’t able to be included.

Also, I would’ve loved to see (from the track testing) the added comparison to a typical forged aluminium, “similar”-weight aftermarket wheel. I think that visual would’ve been big eye-opener... I understand why you didn’t, though.

Just being a nit-pick, but I would’ve used the OEM wheel as a “control” and done another test scenario (“A-B-A”) after the CR wheel.

 

[Trackaholic]

I am a mechanical engineer, but work in the medical industry (cars are one of my hobbies).

I really enjoyed the article, and am in agreement with the general premise that CF wheels are lighter than an equivalently stiff aluminum wheel (and stiffer than an aluminum wheel of similar weight), but if I were to read with the mindset of someone reviewing a technical whitepaper, there are a couple areas that I think could be improved to make the message more clear (and it seems others are picking up on this as well).

First of all, as mentioned in previous posts, to insinuate that all aluminum wheels have the same stiffness is totally wrong. It is true that the material itself will have similar stiffness no matter the strength, but the SHAPE of the wheel has a huge effect on the stiffness, and the manufacturing process has a huge effect on the shape. A typical cast wheel is very limited in spoke design details due to tooling/draft requirements, while a "forged wheel", which is actually typically machined from billet, may have strategically placed undercuts to reduce weight in low stress areas. This allows more material to be placed in areas where it will improve stiffness, while not adding overall weight.

Second, mentioning a single lap time delta was confusing. The largest delta (which occurred on Lap 2, at 0.56 seconds) wasn't specifically mentioned, but neither was the average (.17 seconds). Nor the 40% of laps where the aluminum wheel was slightly faster than the CF wheel. Not sure why the first lap was chosen, but a cynical reader might feel that it was chosen to show the CF wheels in a better light.

While cost was mentioned briefly, the ~$12,000 CF wheels were compared to ~$10,000 aluminum wheels. But one could also get something like a Forgeline (known to be high quality and used extensively in racing), which would be $6600 MSRP and likely less. So, that is a significant difference that probably deserves mention in the article. If the CF wheel was 10% more than a set of those, I'd be much more willing to pay the price. Hopefully in another 5 years...

And finally, empirical data is critical when trying to be scientific, so while there was quite a bit of discussion that made logical sense (deflection for example), the lack of data was disappointing. I liked the photo of the deflection test, but not sure how strongly a flat beam (a small section of the wheel barrel) correlates to a fully round wheel, as the structure is quite different. Having data on a more clearly related test article would be nice.

Again, I really enjoyed the article and thought it did a great job highlighting the benefits of the CF wheel. However, I think some minor tweaks would really help make it seem less biased and therefore reinforce the message even more strongly. Great work overall. It is clear that a lot of effort was put into this, and it does corroborate other reports. Thank you for sharing.

-T

 

[Zitrosounds]

This. The only problem is I need two sets, and my pocketbook doesn't like that, so I have a set of forged wheels for the street. It rains too much where I live to run on only the Cup tires. I wish Ford had offered a 2nd set of CF wheels as an option for some discounted price at the time of purchase. I'd have paid an extra $8-10k for a spare set.

There is nothing wrong with preserving the CF wheels for track duty and having a rotational AL wheel set. I just wanted to emphasize the incredible difference CF wheels make over many AL wheels. I would love to own a set of premium AL wheels for rotational spare. The cost of a premium set of AL wheels is not cheep and my 12 y/o needs braces lol.

 

[PP0001]

A successful carbon wheel aftermarket program will be very unlikely. It currently costs in the range of $6000 to make a set of carbon wheels. That's one style and one fitment.
If you factor in the amortized tooling costs for several styles and a wide variety of sizes and mix in a generous helping of distribution profit margins, and you will quickly be in the $12,000-$15,000 per set price range. There is a very tiny market worldwide for wheels in that price range, dominated by a very few wheel companies with powerful brands and spectacular styling acumen.
Finally is the issue of style. Most carbon designs are just boring or worse, due to a variety of factors. There is an even tinier segment of hard core track guys who don't care about style.
Unless this changes, I would forecast the total aftermarket demand for carbon wheels to be no more than a few hundred sets worldwide.
There will be a few expensive OEM models with carbon, but the aftermarket will be extremely unprofitable to pursue.

I would suggest that for any CF wheel program to be successful from a sales and profitability standpoint the program needs to be predicated towards OEM vehicles and certainly not the aftermarket program.

With respect to us present GT350R owners and other enthusiasts possibly purchasing a second set of aftermarket CF wheels for our cars, that may happen occasionally but that scenario will certainly not keep the assembly line open and viable but if additional manufacturers come on board providing CF wheels as a standard item such as on the present GT350R models there is no question that CF wheels will have a great future down the road.

Regarding production volumes for the GT350R model it is no secret that Ford has already purchased over well 8500 CF wheels from Carbon Revolution in the Melbourne area and once upcoming R model production launches again next Spring for the 2019MY Ford will have purchased well over 10,000 CF wheels from CR which I would suggest is substantial for one model line of Mustang.

It would not surprise me in the least if Chevrolet has or will not look at CF wheels for their upcoming ME Corvettes and I believe that McLaren, Porsche and other manufacturers have CF wheels as standard OEM equipment.

From my standpoint I would suggest that the CF wheel program down under has a very bright future.

 

[BillyJRacing]

A successful carbon wheel aftermarket program will be very unlikely. It currently costs in the range of $6000 to make a set of carbon wheels. That's one style and one fitment.
If you factor in the amortized tooling costs for several styles and a wide variety of sizes and mix in a generous helping of distribution profit margins, and you will quickly be in the $12,000-$15,000 per set price range. There is a very tiny market worldwide for wheels in that price range, dominated by a very few wheel companies with powerful brands and spectacular styling acumen.
Finally is the issue of style. Most carbon designs are just boring or worse, due to a variety of factors. There is an even tinier segment of hard core track guys who don't care about style.
Unless this changes, I would forecast the total aftermarket demand for carbon wheels to be no more than a few hundred sets worldwide.
There will be a few expensive OEM models with carbon, but the aftermarket will be extremely unprofitable to pursue.

Indeed it would be unlikely due to the current challenges of production to be profitable. But that's where Carbon Revolution succeeded. They are a profitable company and are expanding their production 15X. The increased streamlined production should bring per unit costs down in time and as mentioned in the article, will make them more affordable the same way carbon bicycle frames, carbon tubs, and carbon brakes are now attainable by mere mortals.

Porsche is starting to make their own wheels and don't use the same patented production processes as Carbon Revolution. This makes their production costs far greater, and makes it currently difficult to enter the composite wheel market. Your comments don't surprise me and i'm sure many large aluminum wheel manufacturers would push the same misconceptions to deter interest in a far superior technology that threatens their livelihood. But that's the nature of technological advancements.

Thanks, Billy. Great article!

Too bad the temp data wasn’t able to be included.

Also, I would’ve loved to see (from the track testing) the added comparison to a typical forged aluminium, “similar”-weight aftermarket wheel. I think that visual would’ve been big eye-opener... I understand why you didn’t, though.

Just being a nit-pick, but I would’ve used the OEM wheel as a “control” and done another test scenario (“A-B-A”) after the CR wheel.

Thanks. Yes it's unfortunate that I lost that data, but thankfully the tire wear photos weren't lost and they are a far better visual than temp spreads because a far smaller segment of readers would actually conceptualize temp spreads.

Those tires on the OEM wheels were dead. I probably should have done the A-B-A, but those blisters would have made it a frustrating run. Heck, the last few laps were a struggle to keep the times down, while the carbon wheels easily clicked off those lap times and would have done it for another 10-20 laps with ease.

I am a mechanical engineer, but work in the medical industry (cars are one of my hobbies).

I really enjoyed the article, and am in agreement with the general premise that CF wheels are lighter than an equivalently stiff aluminum wheel (and stiffer than an aluminum wheel of similar weight), but if I were to read with the mindset of someone reviewing a technical whitepaper, there are a couple areas that I think could be improved to make the message more clear (and it seems others are picking up on this as well).

First of all, as mentioned in previous posts, to insinuate that all aluminum wheels have the same stiffness is totally wrong. It is true that the material itself will have similar stiffness no matter the strength, but the SHAPE of the wheel has a huge effect on the stiffness, and the manufacturing process has a huge effect on the shape. A typical cast wheel is very limited in spoke design details due to tooling/draft requirements, while a "forged wheel", which is actually typically machined from billet, may have strategically placed undercuts to reduce weight in low stress areas. This allows more material to be placed in areas where it will improve stiffness, while not adding overall weight.

Second, mentioning a single lap time delta was confusing. The largest delta (which occurred on Lap 2, at 0.56 seconds) wasn't specifically mentioned, but neither was the average (.17 seconds). Nor the 40% of laps where the aluminum wheel was slightly faster than the CF wheel. Not sure why the first lap was chosen, but a cynical reader might feel that it was chosen to show the CF wheels in a better light.

While cost was mentioned briefly, the ~$12,000 CF wheels were compared to ~$10,000 aluminum wheels. But one could also get something like a Forgeline (known to be high quality and used extensively in racing), which would be $6600 MSRP and likely less. So, that is a significant difference that probably deserves mention in the article. If the CF wheel was 10% more than a set of those, I'd be much more willing to pay the price. Hopefully in another 5 years...

And finally, empirical data is critical when trying to be scientific, so while there was quite a bit of discussion that made logical sense (deflection for example), the lack of data was disappointing. I liked the photo of the deflection test, but not sure how strongly a flat beam (a small section of the wheel barrel) correlates to a fully round wheel, as the structure is quite different. Having data on a more clearly related test article would be nice.

Again, I really enjoyed the article and thought it did a great job highlighting the benefits of the CF wheel. However, I think some minor tweaks would really help make it seem less biased and therefore reinforce the message even more strongly. Great work overall. It is clear that a lot of effort was put into this, and it does corroborate other reports. Thank you for sharing.

-T

Thank you for reading the article and for your reply. There was never an insinuation that "all aluminum wheels have the same stiffness". The comparison between carbon and aluminum was always in reference to the best "OPTIMAL" design of aluminum. There was a section that mentioned there is only 1 optimal design for an aluminum wheel, and as that design changes for style, stiffness is compromised and the only way to get that stiffness back is to add weight.

Just like anything in engineering, there are multiple ways to skin a cat, but there is only 1 'optimal' design. Yes a forged wheel can have undercuts in low stress areas with geometries that's impossible with cast wheels, but take your optimal forged wheel that weighs say 20lbs (where you can't improve its stiffness with the given 20lbs of mass) and it's significantly softer/less-stiff than a 20lb carbon wheel. Also mentioned in the article, a 20lb aluminum wheel will have its mass spread out more evenly throughout the spokes and barrel, while carbon has its mass more focused in the center - reducing rotational inertia.

The largest delta wasn't the focus. The fastest lap times were, as well as the time difference average (0.17 seconds) on the extremely short 50-second lap. 0.17 second average would equate to 0.3-0.4 second average on most tracks, and I would kill for that kind of advantage in racing. Those middle laps where the aluminum wheel was faster was driving the tires into the ground while trying to maintain consistent laps. The carbon wheels were far easier to turn those laps and I mentioned in the article that I probably should have pushed them a bit harder. Judging by the tire wear I could have easily driven them harder.

Forgeline motorsports wheels are't $6,600. I mention in the article that many companies' racing wheels tend to be heavier and stiffer (and more expensive) than their aftermarket products.

I understand your skepticism of how a wheel segment reflects the stiffness of the wheel as a whole. While it's obvious the whole wheel will be stiffer, the stiffness of the material is still represented and consistent, but at a smaller degree (but similar difference in stiffness). The confidential photos of the deflection of the entire carbon vs aluminum wheel is well represented by the wheel segment photo.

Thank you for your time and feedback.

I would suggest that for any CF wheel program to be successful from a sales and profitability standpoint the program needs to be predicated towards OEM vehicles and certainly not the aftermarket program.

With respect to us present GT350R owners and other enthusiasts possibly purchasing a second set of aftermarket CF wheels for our cars, that may happen occasionally but that scenario will certainly not keep the assembly line open and viable but if additional manufacturers come on board providing CF wheels as a standard item such as on the present GT350R models there is no question that CF wheels will have a great future down the road.

Regarding production volumes for the GT350R model it is no secret that Ford has already purchased over well 8500 CF wheels from Carbon Revolution in the Melbourne area and once upcoming R model production launches again next Spring for the 2019MY Ford will have purchased well over 10,000 CF wheels from CR which I would suggest is substantial for one model line of Mustang.

It would not surprise me in the least if Chevrolet has or will not look at CF wheels for their upcoming ME Corvettes and I believe that McLaren, Porsche and other manufacturers have CF wheels as standard OEM equipment.

From my standpoint I would suggest that the CF wheel program down under has a very bright future.

They are already on the new Ferrari 488 Pista.

 

[UnhandledException]

Typical one sided test obviously funded by the carbon revolution company. Trying to point out the obvious pros and blow them out of proportion.
From that test data, they achieved avg lap speed of 0.17 seconds per lap faster then Oem porsche wheels. In 57 second track.
Is that worth $12k price tag for a set of wheels? How bout compare them to well renowned forged wheels like forgeline wheels that cost about half? Bet the difference will be even smaller and mostly insignificant at that point.
How bout wheel damage repair?
Aftermarket Carbon wheels dont make any financial sense at this point in time other than for show.

This is the difference between a mustang forum which consists of more street smart people with above average practical intelligence than a porsche gt forum which is usually filled with (xxxx insert your adjectives of choice here xxxx).

I have “cheap” made in taiwan aftermarket wheels from signature wheels that weigh about 1lb more than the R wheels and I couldnt have been happier with them. My cost was LESS THAN 1/3 or the cost of these wheels.

Good luck selling these wheels to mustang owners

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