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

[BillyJRacing]

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

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[Ixse]

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.

 

[honeybadger]

@BillyJRacing

Thank you for sharing. VERY interesting read. This brings up some very interesting insights and considerations. The camber compliance bit is particularly interesting. Obviously long-term testing would be needed, but it seems like a CF wheel could reduce your overall budget needed for tires since you'll likely get extended life. Cool!

2 questions if you don't mind.

1. Any insight into how the camber compliance was tested? Would be cool to see wheel manufacturers replicate and share data. The careful word choice of "up to 1 degree per cornering g" implies that some are worse than others. Would love to see the data for wheels many of us are using - be it Forgeline, Signature, Forgestar, 6GR, etc.
2. How long do you think until these will make it into racing?

 

[honeybadger]

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 response seems a bit short-sided to me. Sure - financially they're a big investment. Does the performance justify the cost right now? Probably not for most people. But there is still tons of very valuable, net-new data in here to comb over, further discuss, validate and consider.

 

[BillyJRacing]

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.

There are justified pros and cons in the article.

As mentioned in the article, Forged & Cast wheels have the same stiffness. So if you pick a Forgeline wheel of similar weight to the Porsche wheel, it will have the same stiffness and flex to the Porsche wheel. That's the limitation of aluminum. Maybe give it a closer read; unless you already made up your mind.

@BillyJRacing

Thank you for sharing. VERY interesting read. This brings up some very interesting insights and considerations. The camber compliance bit is particularly interesting. Obviously long-term testing would be needed, but it seems like a CF wheel could reduce your overall budget needed for tires since you'll likely get extended life. Cool!

2 questions if you don't mind.

1. Any insight into how the camber compliance was tested? Would be cool to see wheel manufacturers replicate and share data. The careful word choice of "up to 1 degree per cornering g" implies that some are worse than others. Would love to see the data for wheels many of us are using - be it Forgeline, Signature, Forgestar, 6GR, etc.
2. How long do you think until these will make it into racing?

When driving a tire at the limit, you're probably not going to get another session out of them (most track tires won't last more than 3-4 stints at speed.). For a HPDE level guy, it may, but due to the variability of an HPDE level driver, that would be an extremely difficult thing to test scientifically.

1 - Camber compliance was tested with a machine that holds the wheel stationary and loads the inner rim lip. Unfortunately this is confidential information that I cannot disclose which "big-name, industry-leading" brand wheel was tested or their lab results. Fortunately the tire wear helped to back up those claims. Actually, depending on the weight and design of the wheel, a super-light 'fancy' design wheel can, and have been tested to flex OVER 1-degree per cornering G. For a more general statement that does not take outlying bad designs into consideration, "up to 1-degree" is a more conservative statement.

The main concept is: the lighter the wheel, the more it will flex. The more 'fancy' and 'stylized' the design -going further away from known and common looks of professional motorsports designs (remember: there's only 1 optimal design for an aluminum wheel -and professional motorsports tends to have similar looking wheels for a reason), the more flexible the wheel will be.

The only way to have a stiffer aluminum wheel is to add weight. (Assuming a good design to begin with). The stock, heavy GT350 wheel is much stiffer than the majority of aftermarket 'lightweight' wheels. That's why it's common to see people who switch to those lightweight wheels then say that "This car (GT350) needs 2.5, 3, 3.5, 4* of negative camber and push GT350 (and even R) owners to try to adopt those levels of camber that's unnecessary with a stiffer wheel.

2 - CR is the world-leader in producing carbon wheels and they can't keep up with demand and are expanding operations. Because of that, and the difficulty to enter the market (Porsche is trying), I don't see it happening any time soon. Especially when many pro racing series around the world still mandate iron brake rotors when the cost of carbon rotors have gone down and now make financial sense over iron.

I hope that helps; although I did just state some of the main points of the article. Give it a close read!

 

[Zitrosounds]

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.

Typical closed minded response to a well written article with a data to back it up. The wheels of the R alone are worth the price of admission. And so I did.

 

[oldbmwfan]

I enjoyed it, especially the lap time comparison from a driver who you know is getting what the car and setup can give.

My only surprise was that there wasn't tire probe temp data to support ... the visible wear says a lot, but I would have loved to see that camber loss quantified in the distribution of heat across the tire. So much other effort went into the test, this seems like an easy thing to have accounted for.

I'm not a pro-level driver by any stretch, but I've been seeing pretty even wear on my R tires at -2.5 camber in front (and the car has also been driven by people faster than me).

 

[Epiphany]

Given the pit stops I've witnessed first hand in IMSA Continental I don't see a wheel such as the R model CF unit lasting long when used in a race environment that could most take advantage of it. CF wheels remain far more expensive than anything else as well. The street going CF wheels are pretty but just can't be exploited to their fullest. As to the road cars that actually have CF wheels available for street use you'll note that the story is a bit different when those cars are prepped for far more serious use.

The race version of the Ford GT...

One of Dean's GT4 Mustangs...

What would really have been nice would have been if Ford would have finally dumped MacPherson struts and moved onto a properly designed SLA. Negative camber numbers could have been reduced as that style of front suspension is much better at achieving and maintaining a better contact patch between the tire and a given road surface.

 

[Ixse]

Typical closed minded response to a well written article with a data to back it up. The wheels of the R alone are worth the price of admission. And so I did.

Looks like you failed to understand what i wrote. You are missing the point. Sure its great, R comes with carbon wheels. Im not arguing of its superior stats. The argument here is choosing carbon wheels vs forged aluminum wheels as a aftermarket product.
And the article leaves out 2 of the biggest problem carbon wheels provide, which are cost and maintenance issue.
Also someone else pointed out forgeline wheels have same strength/stiffness as oem porsche wheels. Sure they may have, although quality and design of the aluminum wheel may have differences. Also weight of forgeline wheels are much lighter than oem Porsche wheels. Could that have closed 0.16 sec difference gap? Could be.
You call me close minded? You seem to be the one having hard time critically analyzing whats presented to you. Tell me why the article doesnt emphasize on avg lap time difference, but instead largest delta on a single lap. Also tell me why they decided to use oem porsche wheels that weight more than high quality aftermarket forged wheels?
Maybe instead of just agreeing what you read, do some critical thinking for yourself.
And no, carbon wheels arent worth $12k price tag.

 

[oldbmwfan]

True, I was also hoping to see a comparison of Al vs. CF with less weight difference. You can get wheels in the GT350R size that are forged aluminum and weigh within 3 lbs of the CF wheels. Then you could truly chalk up most of the performance delta to the wheel stiffness, rather than the unsprung weight.

 

[datadatum]

I enjoyed the article. Great photo on page 10:

 

[BillyJRacing]

My only surprise was that there wasn't tire probe temp data to support ... the visible wear says a lot, but I would have loved to see that camber loss quantified in the distribution of heat across the tire. So much other effort went into the test, this seems like an easy thing to have accounted for.

Tire temps are by far the most important factor to determine your ideal camber and tire pressures. I hate to admit it, but the tire temps were lost from the test. Thankfully the pics of the tire weren't lost and really help visualize the camber compliance of the wheel. If we lost those pictures then the whole test probably would have been a loss.

Given the pit stops I've witnessed first hand in IMSA Continental I don't see a wheel such as the R model CF unit lasting long when used in a race environment that could most take advantage of it. CF wheels remain far more expensive than anything else as well. The street going CF wheels are pretty but just can't be exploited to their fullest. As to the road cars that actually have CF wheels available for street use you'll note that the story is a bit different when those cars are prepped for far more serious use.

The CF wheels are stronger and more durable than aluminum. I would have LOVED to have them in the Continental Tire series! #Unfairadvantage

Looks like you failed to understand what i wrote. You are missing the point. Sure its great, R comes with carbon wheels. Im not arguing of its superior stats. The argument here is choosing carbon wheels vs forged aluminum wheels as a aftermarket product.
And the article leaves out 2 of the biggest problem carbon wheels provide, which are cost and maintenance issue.

You repeated yourself twice now and I will again urge you to read the article. (both of those "problems" are addressed in it).

Also someone else pointed out forgeline wheels have same strength/stiffness as oem porsche wheels.

As mentioned in the article: "Strength and Stiffness are DIFFERENT". If the Forgeline wheels are lighter than the OEM Porsche wheel, it will be softer at a fairly linear rate to the reduction in weight. Now the Forgeline wheel may have a marginally stiffer design; but it will likely not offset the big difference from the losses in stiffness due to reduced weight.

Tell me why the article doesnt emphasize on avg lap time difference, but instead largest delta on a single lap. Also tell me why they decided to use oem porsche wheels that weight more than high quality aftermarket forged wheels?

All of those questions are answered in the article's paragraphs.

True, I was also hoping to see a comparison of Al vs. CF with less weight difference. You can get wheels in the GT350R size that are forged aluminum and weigh within 3 lbs of the CF wheels. Then you could truly chalk up most of the performance delta to the wheel stiffness, rather than the unsprung weight.

An aluminum wheel weighing within 3lbs of a CF wheel will flex far more and would kill the outer edge of the tire even worse than the wheels used in this test.

The carbon wheels are worth ~1sec per lap on most tracks on the Ford GT, which has a close to ideal suspension geometry, camber gain, static camber, etc... That's consistent with the results from this test.


I'm more than happy to help answer any questions or clarify any concepts to those who have taken the time to read the article.

 

[Epiphany]

The CF wheels are stronger and more durable than aluminum. I would have LOVED to have them in the Continental Tire series! #Unfairadvantage

I get that CF wheels are "stronger." As to being more durable...I think it fair to say that concern for most is cost to purchase/cost to repair is quite a bit higher than the typical Forgeline wheel along with it being difficult to justify those performance increases given that most R model Mustangs or Ford GT's aren't used in a race environment exclusively across the board.

To my point about how I see them handled in Continental.....I'm sure the guys that change them that have to twist and throw them over the wall at times would welcome a lighter wheel as would the drivers. But their purchase and use would absolutely add additional expense. I've watched how various teams prep their wheels and at times, cringed. A cordless drill with a countersunk bit is used to dress or "freshen up" the tapered area of the lug seat and to quickly remove the glue used to hold the lugs to the wheel. CR's CF wheels use a 6061-T6 male into a female insert here (on all their wheels) to in effect, sandwich the fiber such that you arent having fiber touch either the wheel hub or the lug itself. The last thing you'd want to do is to compromise the insert on a CF wheel. In this regard, Forgelines look to be far less costly and easily stand up to the rigors and abuse in a rather extreme race environment at reasonable cost.

Maybe in 10 years or so they'll be as common as a typical aluminum wheel on a street vehicle. But for now they are way too exotic and owners that have had to deal with any issues can relate to the nightmare situations associated with them. Witness the thread down just a few posts from this one.

https://www.mustang6g.com/forums/threads/gt350-r-carbon-fiber-wheel-failure.104830/

Billy, I had a great conversation with Kyle Marcelli at VIR and your name came up. I could see him getting rated the way you did and getting bumped from Continental in the future. Is there any chance, given the current system, that you'd ever be back in GS (for example)?

 

[BillyJRacing]

They don't use a countersunk bit. They use a conical wire brush to clean off the glue from the lug seats. Carbon Revolution wheels have metal lug inserts so it wouldn't be any different than the interface on an aluminum wheel.

As mentioned in the article, carbon wheels are banned in professional racing, and they would be a significant advantage if they were allowed. 1-sec a lap, heck, 0.5-sec a lap is the difference between 1st place and mid-pack. If allowed, anyone who wants to win would buy them. You just can't make up that kind of performance in pro racing.

He got those wheels fixed and the repair cost was a fraction of a new wheel.

As a Platinum, no. But if I get dropped down to gold then maybe.

 

[Epiphany]

I've seen the bit as well as a brush.

The CR inserts are 6061-T6 aluminum just to be clear. On these wheels they are raised above the face of the CF at the wheel. They are much thinner than the mass of aluminum on a Forgeline (for example). When I'm at my desk I'll post a cut view from CR's patent application that details their design and construction.

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