Monday, February 25, 2008

Catastrophic Failure?

Here is an interesting series of pictures from the race on Saturday showing a crash caused by an R-SYS wheel failure. Or is the R-SYS wheel failure caused by the crash? Run the pictures as a slide show. It is really pretty amazing to see what happens to people and equipment during a crash.
Pace Bend Crash

While it looks like the riders are coming up a hill, they aren't. The photo was taken during the finishing sprint while the riders were doing about 40 mph. The guy with the R-SYS got into the rider beside him and it caused him to jerk his bars sideways. I guess it created lateral pressure on the wheel and instead of the standard taco, the wheel just exploded.

Here is another R-SYS failure featuring Karl Menzies at the Tour Down Under. Karl Menzies Crash. You have to scroll down to the picture in the bar on the left. I know Menzies hit a plastic post, but is it reasonable to expect a failure like that?

Ron, this is a great topic for an engineering mind like yours.


Blogger bluecolnago said...

wow! that's wild! he didn't hit an armadillo, did he?

2/26/08, 4:47 AM  
Blogger oldmanandhisbike said...

All I can say is the guy in the white kit behind him is one lucky fella. Should have run out and bought a lottery ticket after that near miss. His head missed that STEEL fence post by inches! Of all of the place for a guy to crash that could have been bad.
I can't ride hard enough to stress my components to the breaking point! :^)

2/26/08, 5:43 AM  
Blogger jahowie said...

That looked like a really bad crash!! I'm glad that the second guy didn't hit the fence post.

BTW--no it was the GUYS in speedos that inspired me to buy that book!! Real funny...ha, ha, ha.:-)

2/26/08, 8:37 AM  
Blogger chatterbox said...

yikes! Super-scary. That was my guess is that he touched wheels with the guy in front and the lateral pressure of the crash starting is what caused the wheel to explode. Wheel touching = BAD. Esp. at speed.

2/26/08, 2:28 PM  
Blogger CyclistRick said...

Wheels that explode are not a good thing, even if the crash started the reaction. Witnessed a similar situation at a local race (Dunnigan Hills RR) last year when a minor incident involved a CF wheel that exploded into multiple pieces. Guy with the exploding wheel flew into the judges table. Scary stuff. I am a big fan of parts that stay together.

2/26/08, 3:44 PM  
Blogger Donald said...

That just sucks. Moral of the story: My spot at the very back of the pack would have been the safest here. :)

2/27/08, 1:42 AM  
Blogger CyclistRick said...

Been thinking about it overnight .... and am wondering. Years back Ms. Chatterbox had the old Spinergy Rev-X wheels. Nice for triathlons, but the wheels got a reputation for blowing apart. Seems that under some rather common circumstances one of the 8 'spokes' would flex far enough to snap and the load was too much for the other 7 which would start to pop leading to the wheel disintegrating.

Wonder if a similar thing is happening here. One of those CF spokes under high tension pops and the redistribution of the load causes some of the others to pop, and so on as the wheel flies apart. Think I will avoid those puppies.

2/27/08, 11:15 AM  
Blogger Chris said...

Blue - Not that I am aware of, but good thought.

Oldman - brains on the pavement, tonight at 10pm on Fox News.

Jahowie - I will believe you THIS TIME.

Chatterbox - I don't think he broke the spokes by contact. I think it was from the misdirection.

Rick - you could be right. I don't know what kind of tension those things are pulled to. I too think I will pass on these. Plus, how can a giant round spoke be even remotely aero?

Donald - it is safer for sure. But you seem like a risk taker. Get up there and flog it.

2/27/08, 1:40 PM  
Blogger Bike_Boy said...

This comment has been removed by the author.

2/27/08, 2:55 PM  
Blogger Ron said...


Its quite simple. Carbon spokes aren't as good as classic metals (steel or Ti) in handling road bumps. Due to in elasticity, given an out of limits compressive force, carbon spokes can easily break, rather than deforming and springing back. The book The Bicycle Wheel by J.Brandt should make technicalities clear.

This may be a reason why these wheels are made with very "low" spoke tension.

I beg to ask what the whole point of a carbon spoke is. Alarmingly, the total weight of this wheelset still stands at 1300 grams, my cheapo Bontrager X lites are about the same!

Plus, those huge spokes are definitely not very aero, as validated by wheel tests.

Good stuff, I'll note this.

2/27/08, 2:56 PM  
Blogger Ron said...


Rethinking this, I'm not too sure why they chose carbon fiber, but intuition tells me not to use something bad at impacts and zero elasticity on spokes. I made a mention of this today in my blog. Thanks.

3/5/08, 12:29 PM  

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