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Old 12-06-10, 02:13 PM   #1
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Can a broken spoke cause an accident?

I dont' know if this is the right forum, so I thought I would start here. Yesterday in a group ride we had a cyclist go down. The accident happened fast: one moment she was cycling, the next moment literally she was sprawled face down on the pavement. (The cyclist is going to be alright. She had abrasions on her face. An ambulance took to the ER just to make sure). At first we thought she simply lost control, or maybe her wheel brushed against some raised pavement. But, after she left, we examined her bicycle and saw that she had a broken spoke. We then theorized that perhaps the spoke broke before she went down and got caught in the fork, causing her front wheel to stop cold, and then forcing the bike to do a 360. This would fit with the suddeness of the accident. Has anyone heard of this type of accident before? I have been cycling for 35 years and have never encountered such a string of events. Thoughts?
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Old 12-06-10, 02:19 PM   #2
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I've never seen this type of accident but I suppose it's a possible explanation. I expect most spokes are thin and flexible enough that a broken one would bend out of the way if it hit the fork or frame and not be strong enough to lock a wheel.

However, if this was a low spoke count wheel, a broken spoke could throw it so far out of true that the rim hit a brake pad hard enough to either lock or rapidly slow the wheel and that caused the spill.
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Old 12-06-10, 02:26 PM   #3
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Older or the newer fashionable minimally spoked wheel type?

I have always ridden traditional 36 spoke wheels , 32 on smaller wheels
only time a spoke has broken, it is one of the right rear spokes , behind the multispeed freewheel.

my Brompton has a 20/28 spoke pair, but it's a small 349/16" wheel ..

OTOH,
700c race wheel with only 16 spokes and one of the front ones breaks , and

I can easily imagine the front wheel locking up, as it goes widely out of true.

break 1 spoke on a 48 spoke wheel and it goes out of true, maybe 4mm.
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Old 12-06-10, 02:27 PM   #4
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I have never heard of a broken spoke causing a crash, but it might be possible, I guess. But you would have to be pretty unlucky for a spoke to catch in exactly the right way that it jammed a wheel badly enough to immediately stop the bike.

It could also be possible that something got caught in the spokes and this caused the crash and broke the spoke. Or the crash was caused by something unrelated to the spoke, but the impact caused an already weakened spoke to break.
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Old 12-06-10, 02:36 PM   #5
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and she touched no one with a wheel overlap?
just straight down with no contact?
most puzzling indeed.
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Old 12-06-10, 03:07 PM   #6
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Having broken a front spoke on a 16 spoke wheel going 45 mph down hill, I doubt that her broken spoke directly caused the crash. OTOH, she may have panicked when her spoke broke, causing the crash.

BTW, in my own incident, the bike shuddered like crazy and made a racked from the spoke whacking the fork, but the break did not cause it to steer in a any particular direction.
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Old 12-06-10, 04:10 PM   #7
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I'd say that it would need to wrap around and tangle the fork in a way that would be pretty much against chance. A spoke is just too easy to bend and pull through most gaps like a piece of string. Although if a stick got tossed up and happened to jame between the spokes and fork leg that could easily produce such an accident. But on its own if it broke then d jammed the front wheel in such a way as to lock up the wheel it would likely remain tangled and be obvious in the post crash investigation. So it's more likely that she glanced off something or jammed her wheel in a sewer grate or if it was on some sort of loose surface that she jammed on the front brake for some reason but may not remember why due to the stress of the impact.
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Old 12-06-10, 05:07 PM   #8
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I've had a spoke break on my rear wheel and catch the RD, locking up the wheel instantly. Luckily for me all it did was bend the hanger a bit. I don't know if it was a single-spoke failure that got worse when it caught the RD, or if multiple spokes failed at once - I was right at the final max effort part of an uphill sprint interval when it happened so there was definitely enough stress on the wheel if one spoke went a bunch more could follow instantly. I had several broken spokes and a bunch of bent ones when all was said and done.

So I could see a case where a broken front spoke could cause a front-wheel lockup if it were to come loose in a way to allow it to catch the fork.
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Old 12-06-10, 05:09 PM   #9
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I'd say that it would need to wrap around and tangle the fork in a way that would be pretty much against chance. A spoke is just too easy to bend and pull through most gaps like a piece of string. Although if a stick got tossed up and happened to jame between the spokes and fork leg that could easily produce such an accident. But on its own if it broke then d jammed the front wheel in such a way as to lock up the wheel it would likely remain tangled and be obvious in the post crash investigation. So it's more likely that she glanced off something or jammed her wheel in a sewer grate or if it was on some sort of loose surface that she jammed on the front brake for some reason but may not remember why due to the stress of the impact.
Not necessarily - things are going to move around more than a bit if the bike endos and bounces around like the OP implied.
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Old 12-06-10, 05:22 PM   #10
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I doubt that a spoke alone could be the primary cause of an accident, especially if you're talking about one involving an endo. You could alwasy check the fork since if a spoke snagged hard enough to lock a front wheel there's be a mark, and likewise the nipple would be torn partly from the rim (assuming the spoke broke at the hub). It's more likely that something, a branch or piece of road debris got caught in the wheel. If it was a low spoke count wheel, it's even possible a squirrel got caught.

There other possibilities such as a front bearing locking, which is easily checked. Also look for physical marks in the wheel, tire and fork which might yield a clue. My most recent crash was similar to hers in that I was momentarily distracted and caught a ripple in the pavement and lost control. Not wanting to admit that I crashed without cause I claimed it was caused by a gravity wave.
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Old 12-06-10, 05:29 PM   #11
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and she touched no one with a wheel overlap?
just straight down with no contact?
most puzzling indeed.
It's unusual, but it can happen. Just ask Jens.

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Old 12-06-10, 06:03 PM   #12
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It's unusual, but it can happen. Just ask Jens.

My understanding is that TdF crash was caused by a 'fault' in the road coupled with slippery white painted line - not a spoke.
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Old 12-06-10, 06:38 PM   #13
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I was replying to AEO's puzzlement. I posted the video as an example of how a rider can go down suddenly, as Voigt did when he hit some irregular pavement just at the moment he'd taken his hand off the bars.

The OP is speculating that the broken spoke occurred before the fall. Which I think is possible.
The OP and others are further speculating that the broken spoke caused the fall. Which I think is unlikely, even for a low spoke number wheel.

Personally, I think that the broken spoke was either coincidental or caused by the crash, and not the other way around. Occam's Razor and all.
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Old 12-06-10, 06:39 PM   #14
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I doubt that a spoke alone could be the primary cause of an accident, especially if you're talking about one involving an endo. You could alwasy check the fork since if a spoke snagged hard enough to lock a front wheel there's be a mark, and likewise the nipple would be torn partly from the rim (assuming the spoke broke at the hub). It's more likely that something, a branch or piece of road debris got caught in the wheel. If it was a low spoke count wheel, it's even possible a squirrel got caught.

There other possibilities such as a front bearing locking, which is easily checked. Also look for physical marks in the wheel, tire and fork which might yield a clue. My most recent crash was similar to hers in that I was momentarily distracted and caught a ripple in the pavement and lost control. Not wanting to admit that I crashed without cause I claimed it was caused by a gravity wave.
I'm about 90% with FBinNY here...

I can see it happening on a 16-24 count wheel - but even then - you gotta be standing up and leaning forward with the brakes locked for an endo...

Typically when you are in saddle - you are in the best position control and response wise...

I would seriously follow FBinNY's suggestion that you go back and study the incident some more - i.e., look at the eyelet and hub holes, and the spoke and check the scene for an object you folks may have overlooked.

=8-)
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Old 12-06-10, 06:42 PM   #15
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What does she say caused the accident?
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Old 12-06-10, 07:44 PM   #16
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The only way I can see a spoke causing an endo is if it gets wrapped around the axle and jams between the fork and hub body.
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Old 12-06-10, 08:15 PM   #17
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If it was a low spoke count wheel, it's even possible a squirrel got caught.
Funny you should mention that. A few years ago my son-in-law was on a group ride when a squirrel ran right through his front wheel. Actually partly through the wheel as it got caught and slammed against the back of the fork legs. The bike stopped instantly but my son-in-law didn't. He sustained some road rash and a damaged finger that required surgery and still isn't right. The squirrel was DOA.

At the time, we assumed his low spoke count wheel (16 radial spokes) allowed the squirrel to get caught and it wouldn't have happened with a 32 or 36 spoke 3X laced wheel. Wrong. A year later my son was riding home from work and the same thing happened, this time with a 32H 3X wheel A squirrel ran into and partly through his front wheel causing an endo. Fortunately he wasn't hurt as the speed was quite a bit lower but it showed us standard wheels aren't immune to rodents.
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Old 12-06-10, 08:24 PM   #18
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A few years ago my son-in-law was on a group ride when a squirrel ran right through his front wheel. Actually partly through the wheel as it got caught and slammed against the back of the fork legs. .....

A year later my son was riding home from work and the same thing happened, this time with a 32H 3X wheel A squirrel ran into and partly through his front wheel causing an endo. Fortunately he wasn't hurt as the speed was quite a bit lower but it showed us standard wheels aren't immune to rodents.
Are you sure one of your ancestors didn't offend a witch?

Actually though a squirrel can get get caught in anybody's wheel it's far more likely in low spoke count wheels. Speed is also a factor, and the key that determines whether he'll get through, caught or bounced back is the amount of time between the passage of spokes at any one point.

If you want to do a simple experiment try to throw a ping pong ball through a spinning wheel. At low speed a few might make it through, as the speed increases, it becomes progressively more difficult until it becomes impossible. If you have a low spoke count wheel it requires much more speed to make it difficult.
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Old 12-06-10, 08:34 PM   #19
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I had a spoke break on a 36 spoke rear wheel once as I was in the middle of a right turn from one street to another. It threw the wheel way out of true and slammed it against the left brake pad. It didn't lock it up, but it did put a lot of drag on the wheel. I could see it happen if you were perhaps in a fast downhill or something and it jammed it tight enough to lock the wheel up.
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Old 12-06-10, 10:22 PM   #20
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A stick caught in the spokes, throwing her and breaking a spoke in the process. Mystery solved.
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Old 12-06-10, 10:44 PM   #21
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... A few years ago my son-in-law was on a group ride when a squirrel ran right through his front wheel. Actually partly through the wheel as it got caught and slammed against the back of the fork legs. The bike stopped instantly but my son-in-law didn't. He sustained some road rash and a damaged finger that required surgery and still isn't right. The squirrel was DOA.

...A year later my son was riding home from work and the same thing happened, this time with a 32H 3X wheel A squirrel ran into and partly through his front wheel causing an endo. Fortunately he wasn't hurt as the speed was quite a bit lower but it showed us standard wheels aren't immune to rodents.
What's with these squirrels? Last year it happened to me. A squirrel jumped out of the bushes into my front wheel (16 spoke). He went half way around and shot up, hitting me in the chest. He bounced off my chest onto the pavement in front of me. I ran over him with both wheels - dead squirrel. I was luckier.
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Old 12-07-10, 02:02 PM   #22
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FWIW, I've had 3 consecutive (and same side) spokes ripped out on a Bontrager Race front wheel, while riding around 23 mph once. I was seated, riding straight ahead when someone came from behind and to the left on his way to "front and to the right of me" and his R/D came straight into my front wheel before I could react. It happened quickly because he was sprinting for the finish, and I was not.

Even on the low spoke count wheel, a violent collision of spokes with derailleur, I was still able to maintain control and get the bike stopped safely. Incidentally, the rim wasn't even bent from the abuse, and I was able to tear down and rebuild it, replacing the bad spokes, and it's been in service for another 3 or so years now without trouble.

My vote here is that whether it was a popping spoke or an unseen dip/bump/crack in the road that was the trigger, the CAUSE of the crash was an inappropriate response to the 'trigger,' not the trigger itself. My $.02.

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Old 12-11-10, 12:26 AM   #23
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Thanks to all of you for your insight. You pretty well convinced me that the broken spoke did not cause the accident. I am seeing the rider and Sunday. She may have more info. Since she went to the ER from the accident, I didn't have a chance to ask her directly the cause of the accident last week. If I find out I will let you know. Thanks again for your help.

Dave
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Old 12-11-10, 01:07 AM   #24
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I was replying to AEO's puzzlement. I posted the video as an example of how a rider can go down suddenly, as Voigt did when he hit some irregular pavement just at the moment he'd taken his hand off the bars.

The OP is speculating that the broken spoke occurred before the fall. Which I think is possible.
The OP and others are further speculating that the broken spoke caused the fall. Which I think is unlikely, even for a low spoke number wheel.

Personally, I think that the broken spoke was either coincidental or caused by the crash, and not the other way around. Occam's Razor and all.
I've done that on the lips of unpaved to paved roads, but it usually ends up with the wheel getting sucked right out from under you.
the wheel would have to get wedged in a crack or get jammed from something coming between the fork and spokes to cause a full lock and subsequent endo.
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Old 09-07-11, 01:51 AM   #25
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It can. It happened to me. A spoke broke half way down. This meant that when it hit the fork it had enough tension to instantaneously stop the bike from about 10mph to zero.

The mangling of the spoke shows that it broke before and not during the accident. Lessons I can personally try to draw from this are: regular checks of the wheels, always wear a helmet (diving goggles?) and frankly accept and try to prepare for unpleasant events.
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