Very interesting article on carbon wheels

[FormulaMMM]

Parts 7, 9, and 10 in particular.

https://motoiq.com/tested-carbon-rev...iber-wheels/7/
https://motoiq.com/tested-carbon-rev...iber-wheels/9/
https://motoiq.com/tested-carbon-rev...ber-wheels/10/

So I wonder how much factory GTS track testing was done with the carbon wheels?... (See part 10.) Hmmm https://f80.bimmerpost.com/forums/sh....php?t=1335015

Critique of magazine lap time testing protocol in part 9 is spot on and relevant to a certain other endless discussion here in the subforum, and at least one user's expressed opinion in that discussion, but I digress.

[Teeone]

Thanks for sharing. Interesting. I’d like to also see a test that resembles a pothole test. Will the carbon wheel hold up? I like how they made the visual of the wheels, where they show a flex angle of 1 degree actually appear to be more like 15 degrees. However, the tire wear does show the result.

[CanAutM3]

Very interresting article. Thank you for sharing.

[FormulaMMM]

Originally Posted by Teeone

Thanks for sharing. Interesting. I’d like to also see a test that resembles a pothole test. Will the carbon wheel hold up? I like how they made the visual of the wheels, where they show a flex angle of 1 degree actually appear to be more like 15 degrees. However, the tire wear does show the result.

Check out part 5 on strength. Pretty compelling. https://motoiq.com/tested-carbon-rev...iber-wheels/5/

Originally Posted by CanAutM3

Very interresting article. Thank you for sharing.

Nice CS!

[mu2002cs]

There are other posts on this subject on this forum. Will give a brief based on experience. The CF wheels are very strong, but have a serious flaw. On the front, the gap between the brake caliper and the wheel is very small. If you get a build up between the wheel and the caliper, it will score the wheel. Can be caused by track trash or street trash, especially rocks. Once scored, the wheels can deteriorate. Make sure you check your wheels regularly. BMW will replace them under warranty

[FormulaMMM]

Originally Posted by mu2002cs

There are other posts on this subject on this forum. Will give a brief based on experience. The CF wheels are very strong, but have a serious flaw. On the front, the gap between the brake caliper and the wheel is very small. If you get a build up between the wheel and the caliper, it will score the wheel. Can be caused by track trash or street trash, especially rocks. Once scored, the wheels can deteriorate. Make sure you check your wheels regularly. BMW will replace them under warranty

This happens with the standard 19" fronts too. At least one of mine is scored.

You've successfully replaced under warranty? What was the claim reason/language? Thanks

[phantomF80]

Originally Posted by FormulaMMM

Check out part 5 on strength. Pretty compelling. https://motoiq.com/tested-carbon-rev...iber-wheels/5/





Nice CS!

That chart is misleading. A pure carbon fiber tow in the direction of the fiber may have strength near that, but a carbon fiber reinforced plastic composite part will not. CFRP is very strong, but it's very directional with fairly weak interlaminate properties that could lead to delamination. That's the main thing to watch for on these CFRP wheels. When you hit a pothole, the first failure mode will likely be delamination rather than anything in the direction of the fiber.

[FormulaMMM]

Originally Posted by phantomF80

That chart is misleading. A pure carbon fiber tow in the direction of the fiber may have strength near that, but a carbon fiber reinforced plastic composite part will not. CFRP is very strong, but it's very directional with fairly weak interlaminate properties that could lead to delamination. That's the main thing to watch for on these CFRP wheels. When you hit a pothole, the first failure mode will likely be delamination rather than anything in the direction of the fiber.

You're more informed on this than I am. Did you read the entire section on strength? Not buying it?

[phantomF80]

Originally Posted by FormulaMMM

You're more informed on this than I am. Did you read the entire section on strength? Not buying it?

I will say the article overstate the advantages of carbon. I am a big advocate of CFRP, but that also means I am a realist on its pros and cons. CFRP is a orthopedic material, unlike metals. It means it’s strong in one direction, but weaker in others. Also, typical CFRP parts are laminates build up in layers using either carbon tape or carbon cloth, with resins holding the fibers together. Because of this construction method, the properties are weakest between tapes/clothes inside the laminate. It doesn’t take much to trigger a delamination if force is normal/perpendicular to the surface of the part. One issue with this failure is that delamination may not be visible to naked eyes, but may still be big enough to weaken over laminate strength.

In any case, strength of CFRP is tricky to quantify, so I just want to caution people against claims from manufacturers.

[Salespunk]

If you really want to dig into this subject research mountain bike wheels. We have the most testing and understanding of the relative benefits and drawbacks of carbon wheels in the most extreme conditions.

In my personal experience carbon wheels are significantly stronger and more durable than aluminum by every metric. In addition the stiffness and directional flex can be tuned in order to gain whatever characteristics are required. Challenges to carbon are well known, specifically deep scratches that break the strands will create a failure point and the part needs to be replaced immediately. Second is sharp impacts such potholes. My personal experience on this aspect is that any impact that will damage carbon will absolutely destroy aluminum. One other note here is that when carbon fails, it fails spectacularly. If there is an unrecognized issue such a scratch or crack and the wheel is pushed you will see a massive failure when it goes. Because of this it is highly recommended to regularly check for issues especially after sharp impacts (track curbing will not be an issue because they lack sharp edges).

The major caveat here is that the auto industry has way less testing and experience with carbon than the bicycle industry. They do have significantly more resources for testing, but nothing beats real world abuse to understand what normal people will put them through.