Does Wheel Stiffness Affect Performance?  We test Carbon Revolution’s Carbon Fiber Wheels

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There is a lot more to Carbon Fiber wheels than just cool looks and lightweight.  We met up with Carbon Revolution at Las Vegas Motor Speedway to learn about their game-changing technology and were blown away how important wheels are to the performance of a car, affecting everything from steering feel to overall grip and noise/vibration/harshness (NVH). We then conducted a proper back-to-back test of their CR-9 carbon wheels against high-end OEM aluminum wheels on a $100K+ sports car to see what real-world performance and lap time improvements can be achieved from carbon fiber wheels.

Carbon fiber is an incredible material. Not only for its extremely high tensile strength, stiffness, and low weight of the carbon fibers, but because of the endless possibilities those fibers can be weaved and positioned to specifically engineer strength and stiffness within a component in ways that are impossible with traditional materials.

What does this mean when applied to wheels? Not only can a carbon fiber wheel be made lighter and stronger than traditional forged aluminum wheels, but they can be substantially stiffer and make for a quieter ride, among other advantages. We learned that ultra-lightweight aluminum wheels can flex and lose over 1-degree of camber for every cornering G-force the car can generate.

From our testing, a high-end OEM aluminum wheel severely blistered the outer edge of the tire due to the wheel flexing and a lack of static camber. Meanwhile the extremely stiff Carbon Revolution CR-9 had significantly better tire wear, zero blistering, and was consistently faster on track. Because of this stiffness, carbon wheels can run less static camber than aluminum wheels. This improves braking, acceleration, and consistency.

Carbon Revolution is the world-leader in producing carbon fiber wheels and the first company to supply carbon wheels on a mass-produced OEM application. They have successfully merged aerospace processes and technology with the efficient process controls of high-volume automotive manufacturing to exceed global OEM quality and performance standards.

Created from an independent R&D program that provides technology mentoring to Formula SAE teams, the first composite wheel appeared in 2004 on F-SAE cars and made their way to OEM applications in 2016.

Carbon fiber composites are a game-changing material whose versatility and properties allow for endless possibilities of use. Carbon is an ideal material due to its light weight, strength, and durability, which is paramount for safety in everything from racecars, fighter jets, passenger planes, to sporting equipment and medical devices.

Carbon fiber wheels represent a paradigm-shift in performance and the physical capability of what a wheel can do because of carbon fiber’s versatility, durability, and strength-to-weight ratio exceeds what is possible with metals. While forged aluminum wheels have been the gold standard for decades, carbon fiber has significant advantages over aluminum and even magnesium wheels.

We are now going to dive into the technology that is incorporated into carbon fiber wheels, how that technology far surpasses what aluminum is capable of, and learn more about the importance wheels play on everything from performance to ride and handling. We will then go over data from a proper back-to-back test of high end OEM Aluminum wheels vs Carbon Revolution’s carbon fiber wheels.

This is a very technical article and I may lose a lot of you. If that’s the case be sure to thoroughly read “Camber Compliance” on page 7.

Table of Contents:

Page 1 – Intro
Page 2 – Carbon Fiber Wheels used by OEMs
Page 3 – Benefits of Carbon: Lightweight – Rotational Inertia
Page 4 – Benefits of Carbon: Lightweight – Gyroscopic Effect
Page 5 – Benefits of Carbon: Strength
Page 6 – Benefits of Carbon: Stiffness
Page 7 – Benefits of Carbon: Stiffness Coninued – Camber Compliance* (Must-Read)
Page 8 – Benefits of Carbon: Durability, NVH & Cost.
Page 9– Important Factors for wheels on Racecars & Track Test Procedure
Page 10 – Wheel Weights, On-Track Testing, Data/Laptime/Tire Analysis, and Conclusion

31 comments

  1. Good article covering lots of different areas. It would be interesting if in the 911 test, the camber was optimized in each case and THEN compare lap times, tire wear, and what the static camber numbers ended up being. Perhaps your lap time differences could be equalized with more static camber for the aluminum wheels. But yes, the tire wear was a good demonstration of the difference in wheel stiffness and camber change.

    In your opinion, is there any downside to carbon fiber wheels on a race car aside from cost? They would be fine with the heat for a couple hours stint? No concerns about impact loading or how they would fare in a smaller crash (e.g. an aluminum wheel would bend and get you back to the pit, carbon fiber would shatter)?

    1. More static camber might equalize things in steady state cornering but being able to get away with less camber means a flatter contact patch for better braking and acceleration in addition to not having to deal with camber issues like tramlining and surface mu sensitivity under hard braking.

  2. This is one of the most interesting articles I’ve read on this site in a while! I’m still amazed by how much the aluminum wheels can deflect.

  3. regarding camber compliance; How much influence does wheel size itself have on camber compliance? the article states that wider tires require less static camber, but what about different diameters of wheels? for example would 17’s require less static camber than 19’s?

    1. Diameter does not have as big of an influence on camber as width does. But as the diameter of a wheel increases, it becomes difficult to maintain stiffness without proportionally more weight. An ultra-lightweight large diameter wheel (say 19″) will be far more flexible than an 17″ wheel of similar weight and will require more static camber due to the increased camber compliance.

  4. Interesting, but more an ad than an actual review. Carbon fiber is nice, but still years away from being actually affordable, if it ever is. No mention of the cons anywhere. Like what happens if you hit a big pothole? You can always have an alloy wheel fixed. Try that with CF.

  5. In conclusion, make sports cars a proper weight, like 2300-2800lbs and equip with 16in wheels and well-boosted hydraulic steering and a set of $875.00 aluminum flow formed wheels will work as well, and don’t put the engine in the rear like that dopey beetle you drove….and voila, problem solved, and have more fun driving.

  6. One of the better automotive engineering/technical articles published online ever.

    FYI, the spindle/bearing/hub compliance on a typical passenger car during cornering is also around 1 deg per G. Most door-slammer race cars with sticky tires are way overloading the OE wheel bearings and flexing them too much. So lots of potential gains to be had in terms of camber/toe compliance with stiffer wheel bearings or stiffer structures on both sides of the wheel bearings.

    Thank you Billy/Mike/MotoIQ for doing these fantastic articles!

    1. Hi Bill, do you have data for the hub deflection? I was wondering because I often fight this when working on production-based racing cars due to its effect on piston knockback on the brakes.

      1. No data, only memory. I had a friend 15 years ago who did a year-long benchmark project to measure competitor suspension compliance for a Detroit OE, he probably did 20 cars total. I saw him measure the data on a big flat-plate rig embedded in the floor. He removed the wheel/tire and replaced it on the hub with a stiff alignment-type stand, this allowed visual access to most of the suspension components behind. He put little dimensional measurement balls at all the connection points between parts. Then used optical 3D measurement to measure the position of everything before and after various load cases (simulated 1G cornering, simulated 1G braking, etc.). This allowed measurement of total deflection at the hub and how much individual components were contributing to it. Sort of a poor-man’s K&C machine, but it also gave all the intermediate contributions rather than just the end result.

        He said there was pretty consistently ~ 1 deg/G camber flex in the upright/bearing/hub. I don’t remember if he had a measurement point at the caliper mounting ears, this would be relevant to your brake question.

        Also, he didn’t know if camber/toe stiffness was consistent among competitors because it was a targeted parameter for suspension design, or if the stiffness just consistently worked out that way after all the other needs (cost/reliability/weight, etc.) had been addressed. Yes, he was relatively isolated from the suspension groups he was feeding the data to.

    1. No, and they do not sponsor the site either. This was an independent test that I only agreed to do once they met all of my criteria for a proper (and expensive) back to back test. Expensive because I didn’t want to conduct the test with wheels with differing widths (even 0.5″), differing offsets, 100* weather, different times of the day, etc…

  7. Moto IQ has become more and more paid spots basically masquerading as reviews. You all have to make a living, I know, but there is a lower percentage of real content vs. paid content these days. I read the site less and less…

    1. The concept of stiffness and its effect on camber compliance applies to all wheels. There are a lot of concepts and take-aways from the article that can be used to make better, more educated purchases of ANY wheel.

    2. What do you oppose about this article? I felt Billy did a great job:
      – of explaining the science/physics behind the benefits of low mass wheels
      – some cool real world example demo videos,
      – showing the material property differences
      – how stiffness affects camber performance (which I never thought of nor seen anyone else talk about)
      – executed a well thought-out test plan
      – even if you didn’t believe the lap times, the last picture doesn’t lie.

    3. As far as I know, they didn’t pay Billy anything. I don’t even think he got wheels out of this or anything at all other than he did it for his curiosity. I know they didn’t pay us anything to do it.

  8. I am curious about what you consider “real” content, I mean there are only so many times that you can kick a dead horse. on the subject of suspension setup, I would consider that subject covered by moto IQ already. Yes, i would love to see more garage tips articles, as well as maybe an engine building series of articles. The question then remains what else can they write about? Product reviews, event reviews and project cars? If there are more then please chime in to add more but from the sounds of it people are considering product reviews to be “paid” articles. Then there are project cars which often have sponsored parts in them, so people will also consider those to be “paid” even though on top of all the other costs of running this site there are costs to the parts. Finally there are event reviews, personally this is something i would love to see more on from the motoIQ staff. since these events are usually heavily sponsored by companies, would the general consensus be that they are paid articles? I dont know but i would like to see MotoIQ do a break down of shows such as Import Alliance and Gridlife. Another article series i would like to see is a MotoIQ write up on all of the different tracks around North America like Frank has been doing for the west coast.

    So what else would you consider “real” content?

    1. I had a column called “Fast Lap with Billy Johnson” and I put a lot of time into those track notes; something I get paid to do when I coach but am giving the information out for free. Those are some of the least popular and lowest viewed articles that i’ve written, despite having more time invested in writing them.

      I guess some people just want negativity and criticisms of products rather than focusing on the positives. I agree that there is some loss of a review being ‘genuine’ when there are no negatives to a given review or car, so it’s a tight rope to walk.

  9. Too bad there isn’t much options in 17″ or 18″… Never would have guessed good rims/wheels did THAT much of a difference!
    Also found the post about tyre size very informative, thank you for sharing 🙂

  10. As far as I know, they didn’t pay Billy anything. I don’t even think he got wheels out of this or anything at all other than he did it for his curiosity. I know they didn’t pay us anything to do it.

  11. My concern more than anything, (great article by the way) is kinetic energy.
    Let’s take this Porsche GT3 for instance, which hits a pothole at 80mph causing a X kilo-newton of force to bend or deform the rim. (I use kilo-newton for the sake of the explanation).
    While the OE alloy wheel would bend or break, (not sure if those GT3 wheels are cast or forged, it doesn’t matter really)…..the OE wheel would be damaged while the Carbon wheels wouldn’t?!?! Or to a lesser degree….
    Well, it is impossible to eliminate kinetic energy, therefore that force would have to transfer thru the wheel bearings into the hub carrier, hub, into the shock…..somewhere that shock, SOMETHING would give up. It could be the spindle, a control arm, or even the damper…..causing to crash.
    At that point you ask yourself: yes I spent $12K on bling bling wheels that CAN take the force and the abuse, but I crashed because something else gave in.
    I have a really hard time believing that the carbon wheels would suck up/ absorbing all the kinetic energy when hitting a pothole, (or something of that nature). They can cope better, yes….but to eliminate kinetic energy, not a chance.

    1. the way I see it, if you can afford to drop 12k on a set of wheels, you can afford to replace wheel bearings or hubs or whatever… also the tire absorbs a lot of kinetic energy, one of the reasons I don’t like running rubber band no sidewall tires…

  12. Great article! I love reading stuff like this. More technical articles like this are needed in our overly “showy” scene. I like to know what actually makes a part better and how it works.

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