Jim’s Tech Talk
By Jim Langley
This week I’m sharing photos of what I think is a fascinating wheel collapse or as chefs say, “deconstruction” might be a more appropriate word for what happened.
Follow-up on Chain Keepers
But first, a couple weeks back we were talking about getting a dropped chain back on when a bike has a chain keeper (a device designed to keep the chain on that can still allow the chain to drop under dire circumstances).
I just wanted to let you know that there was so much interest in that story that I decided to make a separate video about installing a road bike K-Edge chain keeper. Here it is below. And, since several folks already asked, the video is about braze-on/bolt-on front derailleurs. If you need a keeper for a clamp-on (band-type) front derailleur on a standard round tube frame, Deda Elementi makes the Dog Fang (great name) https://amzn.to/3Myo4sK It’s easy to install and adjust.
Mike’s Wheel
Now for Mike’s wheel story. Please refer to the photos as you read along, weigh the evidence and see what you think happened. There are some obvious lessons (don’t hit things in the road) and maybe some other things worth remembering.
Mike is a Santa Cruz roadie friend of a friend of mine who sent him my way for advice. When I talked to Mike on the phone he said he’d had a bad accident in which he broke one elbow and almost broke the other too. He explained that he somehow didn’t see a stick on the road and when he hit the stick his front wheel collapsed. He said he didn’t have any time to react and he fell straight down onto the pavement landing on his elbows!
The Stick
You can see the stick in the first photo. Look closely and you should be able to see the black marks in the stick from the spokes. From the way the spokes marked up the stick and from the fact that there didn’t appear to be any marks on the front of Mike’s carbon fork, I believe the stick got flipped into the wheel when Mike hit it and then it jammed sideways between the fork and spokes.
But Mike didn’t get thrown over the bars, he was dumped straight down onto his elbows. So I think the wheel must have kept turning while the stick was still in the fork. Some spokes are bent and some of the aluminum nipples are torn, too, which indicates that a lot of force pulled on both.
Deconstructed Wheel
In photo two notice that the wheel basically came apart at the hub. It’s built with direct-pull (also called “straight-pull”) spokes. Mike’s have wedge shaped heads that fit into pockets in the hub. The hub is slotted to receive the spokes. When the wheel is tensioned the spokes are held in place in the hub by the spoke tension and by how the spoke heads fit into the pockets.
There are direct-pull spokes that pass through the hub so that they’re held captive in the hub and can’t come out unless they break or the spoke nipple comes off. But Mike’s hub is slotted meaning when loose the spokes can come out of the hub.
There are plastic dustcaps that snap over Mike’s hub. One is shown in photo three (the one that belongs on the other side got lost in the crash). The dust caps are what ensure that the spokes can’t come out of the hub if the wheel suddenly loses tension. Notice that the one dustcap still there is loose on the hub now. Also look at the hub spoke hole at about 12 o’clock on the hub. Notice how it’s stripped or spread open.
Total Collapse
Looking at everything I think what happened is:
- Mike hit the stick and it got sucked up by the wheel and jammed between the fork and spokes.
- The bike kept rolling and as it did so several spokes ran into the stick which put so much force on the spokes that their ends were yanked out of the hub holes, ruining the hub in the process.
- Here’s where it gets interesting. A few loose or broken spokes won’t cause a wheel to collapse. But when Mike’s spokes got yanked out of the hub, the ends of the spokes must’ve been shaped just right to pop off the very dust caps designed to keep the spokes in the hub.
- The result was that the wheel lost almost all spoke tension and almost every spoke came out of the hub as you can see in photo 4
What I find amazing is that it happened so quickly. Mike said he only had a second or two to react and he also said he was only going about 12mph. I would have expected it to take several revolutions for any wheel to come apart like this. But I believe it happened the way he said it did.
Am I Right?
I look forward to your comments on whether you agree with my theory or have another one. I also think it’s worth considering what wheel lessons can be learned from this. As I said at the start, we can never be too cautious about avoiding things in the road. But, equally important I think is the quality of the wheels we choose to ride.
The problem is, how could Mike or his mechanic or the bike shop have known that those plastic dust caps weren’t up to the task of keeping the spokes in during such a crazy calamity? I don’t think they could but the wheel manufacturer should have, don’t you think? If nothing else, now we know to look even more closely at how spokes are held in our wheels!
And what about Mike? He’s healing and looking forward to getting back to riding with some different wheels.
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.
Stick into spokes, all spokes losing tension, and the whole wheel collapsing inside of single revolution sounds nuts but I can’t really imagine what else might have happened. The 12 MPH speed at the end of the post is a surprising twist — I pictured somebody speeding downhill on one of our mountain roads when he was surprised by storm debris in the road, as I’ve been paranoid about this myself.
you have to be 100% right
i have never seen those slotted hubs before
what a nightmare, what is the reason for those?
if the first spoke had not come out, the stick itself would have probably broken and at most one spoke would be bent – even one broken usually doesn;t collapse the wheel..
Why I ride 3 x 32 wheels for 60 yrs +/-, although I never had a stick in the spokes.
If the spokes and hub hadn’t given way then the rider would likely have gone over the handlebars, or the fork (was it carbon?) may have given way. I’m having trouble picturing a failure scenario that I would prefer. They all seem very painful.
Back to chain keepers, I used to drop my chain a lot when I rode a high-wheeler recumbent, with a chain 2 1/4 times the length of a diamond frame. Now that I am a regular bike frame rider, I almost never drop one. The only time is when I’m cleaning the chain on the work stand!
I once rode over a stick that I deemed too small to worry about but that little stick flipped into the spokes and was carried to the fork where it broke with a loud noise. I am lucky that the spokes were strong enough to save the wheel but I no longer take small sticks for granted.
Jim’s photo of the stick makes it look more like a major branch of a tree. No way would I run over something that big!
I’ve been a bike mechanic and cyclist for over 40 years and seen lots of crazy broken bikes and parts come into shops where I worked. I don’t think a different wheel design or specifically the hub to spoke attachment would have changed the catastrophic outcome of a stick getting into the wheel. My only observation is that radial laced, low spoke count wheels, do leave a larger opening for an object to enter between the spokes than a cross-laced higher spoke count pattern that might have possibly deflected the stick instead of allowing entry into the wheels spoke path.
Never good to hear about a cyclist injured in a crash, but thanks for sharing info that may help others.
I’ve had 2 ‘big stick into spokes’ crashes over the years but in both the wheels & I luckily held up enough to finish the rides. One was with an MTB wheel with 24 straight-pull spokes (totally undamaged) and the other an old-school 32-spoke road wheel (stayed true for the ride but needed 2 spokes replaced).
Gotta agree with Jim about questioning those plastic dust caps but could the hub’s apparent limited metal engagement lip holding the spoke head in place also be a factor in the spokes coming out of place? After reading this report I went straight to the garage & carefully inspected my family’s 4 wheelsets with straight-pull spokes (different makers) for any defects. FWIW- I noticed all have larger spoke-holding lip areas in the hubs than what the pics of Mike’s wheel seem to show.
Couple questions- How big is Mike, and were there any problems with the wheel before the incident? I have read about a wheel tick or creaking noise being caused by a crack in the hub at the spoke interface.
After seeing the aftermath of “stick in the spokes” accidents and narrowly avoiding some myself, I learned:
– Avoid riding over sticks whenever possible.
– If you can’t avoid a stick, aim for the middle, as it won’t flip into your wheel.
Hitting a stick at or near the end can cause it to flip up and possibly get into the spokes. There’s a possibility that a stick will break if you roll over the middle and still flip up, but if it’s that fragile, it probably won’t lock up your wheel. Your odds of avoiding a crash are better, if not 100%.
I’ve built a few wheels for myself. The last one I did was a straight pull front wheel. It was kind of a pain to tighten the spokes – I had to use a soft-jaw plier to keep the spoke from turning when I tightened the nipples. I decided I’d rather just stick to j-bend spokes after that, and now this story has convinced me that that was a good decision! When the spokes were forced inward from the contact with the stick, it would have caused the end of the spokes at the hub to push outward, so it looks like one pushed through the side of the hub spoke hole, which then caused a cascading failure, with the other spokes able to push out towards the center of the hub and out of their sockets.
Striaght pull spokes and hubs need a re-design – the spoke should have something that keeps it from spinning, and the hub needs to be designed more robustly so that the spoke can’t break through the side of the spoke well like that.
Had a 28 mph crash when an industrial box lid blew into my front wheel. Broken collarbone for sure, but same wheel as in this story was not even out of true. I am 175lb and the GPS recorded the speed.
My wife ran over s green pine cone which flipped over and got caught between her front when spokes at the inflation valve. When the line cone got the forks it twisted and sheared the inflation valve off. The explosive decompression of her front wheel was quite loud.
We replaced the tube and finished our ride. A week or so later, as she was cleaning her bike, she noticed that there was some delaminated carbon on the inside of her fork. We took the bike to the LBS where we purchased the bike and they stemmed to order a replacement fork. Surprisingly a suitable replacement could not be found so we ended up having to but her a new frame.
I never would have thought that a pine cone could total a bike.
Cautionary tale;
As a starving grad student, I ordered a sweet 1975 Gitane in Burgandy red with gold highlights. The iron-cottered crank was upgraded for a hilly RAGBRAi. The simplex derailleurs wore out (they never were worth a damn). But the Bluemel fenders lived on and on, even when they became cracked with age. Modern fenders have break-away stays, but not so with these 40 year-olds. As some readers mentioned, hitting a stick off-center flips it neatly into the spokes, then up to the fender stays and on to the fork crown. The front fork bent, the frame bent, my chin did what the oral surgeon described as de-gloving. The DEA Superchrome wheel is still in service (on a replacement frame and fork).
I’m wondering what the spoke tension was prior to the stick hit the wheel? Was the stick collision enough to unseat some of the spokes from the hub leading to a chain of events leading to the collapse of the wheel.
Forced into a pothole by traffic, I have had spokes come out of the slotted rear hub on my older KYSIRIUM wheels. At low speed, I got the front wheel over the pothole but the rear wheel hit HARD. I walked to a bike shop where I borrowed a KYSIRIUM spoke wrench. I was able to loosen, re-install undamaged spokes and true the wheel. Unbelievable that the rim wasn’t bent. I finished my ride!
As most cyclist know riding on busy street and roads with traffic can be very dangerous, I’m sorry to say danger is just part of the sport of cycling wether on road or off. I’m 78 and have been riding for fourty years. I have had a few spills. After bi-lateral knee replacement 15 years ago I gave up running and started riding more. The advice I give people is try to be more aware of what’s in front of you when you are out riding.
Rex. That’s amazing! Glad that you were able to fix it and continue on!
I agree with others, you’re right about what happened.
I had the same thing happen to me about 30 years ago, but in those days we had steel bikes and 36 spoke aluminum wheels and hubs, the spokes actually cut the stick in half, and broke 3 spokes, but no other damage to the wheel, hub, or fork. I twisted the spokes around other spokes, deflated the tire so I could readjust all the spokes the best they would get, opened the brake release lever, reinflated the tire, and rode 18 miles home with a slightly wobbly bike.
Had a friend who had a squirrel run at his front wheel, and cut the squirrel in half, yeah, it was a mess and broke 2 or 3 spokes, but without any tools he had to walk 6 or so miles home. There was blood, and crud all over that front wheel, fork, and downtube, he was a bit squeamish so I cleaned his bike!
Stranger things can get into your wheel. My LBS had a bike come in with a squirrels head jammed into the fork.
A new way to get squirrel for your stew? Or vegetarians can ride through cornfields…?
I don’t often disagree with Jim, but here is what I think happened. 1) Stick flips up and through wheel. 2) Stick rotates with wheel until it hits crosswise to the fork, not wedged. But if might be either. 3) Stick stops and spokes break/pull out sequentially as they impact the stick until the wheel collapses which would happen in approximately 1/2 revolution. If you look at photo 2 it appears that at least 8 spokes are all bent near the outer end where the stick impacted them.
A stronger hub/spoke arrangement might have altered what broke, but probably not the result. I watched a friend get taken down by a stick flipped up by another bike. In that case the wheel remained intact but the fork snapped and he did a sudden face plant. Even if the bike is strong enough to survive this you will still fall so the only good answer is to be observant.
Jim – a fellow Tucson cyclist sent this pic to me a few years ago. Fortunately the cyclist did much better than the unlucky squirrel. I heard he might of been descending Mt. Lemmon, have not confirmed. Depending on season, skunks & squirrels often cross our gorgeous mountain road.; almost always on our descents.
I did the same thing in a different era
50 yrs ago so a steel Raleigh
Complete lock up on front wheel
I go head over heals, land on both forearms
Thought I broke both arms
Few days later I’m fine ! Youth !
Front forks bent back, not a big deal to replace
Surprised I survived childhood
I’ve heard that the thing to do if a squirrel is hesitant to go one way or another is to just aim at the animal. It will get out of the way. True? I’ve been too afraid to test it out…
Craig A—- That’s my general strategy for dealing with small animals in my path. Some time ago there was an ad campaign for safer (car) driving in deer country to help minimize collisions- “If you see a deer, DON”T VEER”. Logic was (1) the animal was just as likely to jump in the direction of your avoidance turn thus causing a collision AND (2) too often the driver jerks the wheel to avoid the deer, loses control, & crashes themselves. An additional consideration for a bike rider is that your tire traction if unfortunately hitting a small animal is like hitting a patch of ice- your best chance of staying upright is by holding your line & coasting over it.
Personally- When I see an animal I slow while holding my line, call out to get the animal to move, and then steer smoothly in the opposite direction the animal chooses to flee. In decades of road riding I’ve never yet hit an animal because it just stood there in my line.
It is surprising what you can survive if the bike stays upright. I once had a small dog run right in front of me and rolled over it without falling. And yes, the dog was OK.