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Discussion Starter #1
I remember many years ago when two of our esteemed members, Mark Buckelew and Martin from Motowheels had one heck of a prolonged argument over a BST wheel failure at a race track. Sadly both of those members have passed away but this made me have memories of that:
https://www.instagram.com/p/BdpyXbghwzt/
 
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Retired Pipe Polisher C2H6O+
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Is the photo from their debate or is this a new occurrence?


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This popped up yesterday. Possibly the bike it came off? (Joking)

Would love to know more about the incident that led to this happening....
 

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As a fan of BST products, I hope there were other forces involved..!..?
 

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I’ve seen mag and aluminum wheels just as bad. I’d like to hear more also.


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Discussion Starter #9
This is a new incident. Some are saying that the rear brake was the cause, that it was red hot from locking it up.
 

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I think I found the thread Scott is talking about. It's a fun read and very thought provoking. Some of the arguments get a little long winded but I speed read those. :)

http://www.ducati.ms/forums/56-superbikes/26849-carbon-fiber-wheels-ducati.html

I have some experiencing at crash testing aluminum wheels. I'll have to let you know how the carbon fiber wheels hold up if they are ever so unlucky. :)
 

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I'm curious to see what else could be at fault. I've had some pretty gnarly get-offs but never had a wheel detonate like that.
 

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Just something any of you considering a composite material wheel should keep in mind... CF layups are incredibly strong up to yield. Once yield strength has been exceeded however they go almost immediately to ultimate tensile and come apart, like what you see in that first image. Al alloys (and to a lesser degree Mg) have more predictable non-linear behavior, as seen in the images that @DuckMan posted, and therefore offer greater protection against catastrophic failure.

Essentially your decision should be based on your use case... If you race, and need to shave every available gram of mass, then the attraction of a pair of CF wheels is understandable. If however you are just looking to adorn your machine with the latest bling, then at least do so with the knowledge that if something goes wrong, e.g., brake lock leading to excessive temperature buildup, this type of failure is a possibility.
 

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I would have to say that in my incident that wheel material was totally irrelevant. The end result would have been exactly the same. Fall down and go boom.

But come on. A brake lock up generating enough heat to cause the wheel to fail. I would say that's not very likely.
 

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I would have to say that in my incident that wheel material was totally irrelevant. The end result would have been exactly the same. Fall down and go boom.

But come on. A brake lock up generating enough heat to cause the wheel to fail. I would say that's not very likely.
If by "end result" you mean that the wheel was a write off, then yes, I agree. A forged or cast alloy however is not going to suffer delamination and come apart like this one did. That's all I'm saying. Oh, and I guarantee that prolonged exposure to excessive temperatures, e.g. temps such as those which would be generated by an event such as brake pad binding, will ultimately lead to a material failure in a CFRP, or other similarly constructed composite structure.
 

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I don't know what you hit, or how large it was so I'm not going to speculate on your particular incident. Although I'm glad you came away (relatively?) OK.:grin2:

About 3 years ago I hit a rock on my BST equipped ST4S. I was in and out of shadows and didn't see the rock (it was about 4 inches square) until it was too late. Luckily I managed to stay upright.... The hit was hard enough to embed chunk of the rock into my front tire (wish I had taken a pic of that).

No damage to the BST - I thoroughly checked it afterward and have subsequently put about 20,000 km on that rim.

I have seen the damage caused by 2x4s and other smaller items to aluminum rims. I'm absolutely convinced that had I been running an aluminum rim when I hit the rock the rim would have been significantly damaged.

From everything I have read BSTs are stronger and more resistant to damage that aluminum wheels in the plane forces are expected. My experience bolsters that belief.

I would have to say that in my incident that wheel material was totally irrelevant. The end result would have been exactly the same. Fall down and go boom. ...
 

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There is no question in my mind that today’s carbon fiber wheels are stronger than their alloy wheel counterparts. Their main drawback is that they can be damaged internally in a number of ways, so just a visual inspection is insufficient to assure their continued safety.

At its strength limit, carbon fiber reinforced resin cracks - which causes it to loose structural integrity, whereas metal stretches and then breaks after the amount of stretch becomes too great.

It’s obvious that a dented, cracked or bent metal wheel has been damaged, and it’s easily determined using X-ray and liquid penetrant inspection whenever you have fabrication problems such as casting voids or internal cracks caused by fatigue failure or crash damage.

I’m mainly concerned about damage that can occur after the carbon fiber wheel leaves the factory, and I’m particularly worried about undetected damage caused by conventional tire mounting equipment and untrained operators. To my knowledge, they’re currently all untrained operators since the wheel manufacturers have not provided any specific guidelines on how—and how not—to mount tires on their wheels.

Further, damage from road hazards will not always be to visible surfaces and (again, to my knowledge) the manufacturers provide no useful inspection methods or acceptance criteria to the owner.

What’s a good criteria for determining significant damage to carbon fiber? We don’t really know yet. For example, Boeing designs and builds a lot of carbon fiber structures defines Barely Visible Damage as impact damage that results in a 0.10 inch long defect that is visible from three feet away. Boeing says that the impact that causes Barely Visible Damage is sufficient to affect the structural integrity of the underlying CF structure.

That said, if I hit a large object or pothole in the road I’d be very concerned about continuing to ride on a carbon fiber wheel. I’d certainly avoid buying a second-hand carbon fiber wheel or any wheel involved in a crash.
 

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I suppose there is a possibility that a CF wheel can sustain damage that an external inspection would not reveal - although I think it unlikely. The material just isn't that thick. I think (purely my conjecture) that if there were any significant damage would cause some sort (be it a crack or bubble) imperfection in the resin. Also, the wheel will not instantly go from invisibly small internal stress to major delamination/failure.

Yes, tire changes are a significant concern with BSTs. Since the ST4S is my long distance bike I often need to get tires changed away from home. I've had shops deny me service because they were afraid of the CF wheels - "We won't touch them because they can shatter even if we do everything right..." In fact I had a wheel ruined by my local shop during a tire change. They were great about it and replaced the rim. By treating me so well they have a lifelong customer in me...

Do BSTs have unique challenges? Yes. Do the benefits outweigh the challenges? Absolutely!

RobertVP
 
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