[don simon fbpe]

I managed to get spat off the bike last week and and looking for possible reasons. I’m not in a current state to look around the bike as the broken shoulder and muscle damage on right leg is somewhat restricting.

Riding along at about 30km/h and the rear wheel locked up. this caused a slide which ultimately high sided and spat me off, I got back on and rode a further 1.5km. Nothing obviously broken on the bike. Rear mech intact, so not too sure if chain had jumped off the cassette. No potholes, no obstacles. It was an immediate and violent action from the bike (which makes me think that no stress was put on rear mech or hanger) and I’ll give it a good look over when more mobile. No one else was involved.

Any thoughts of the cause in the meantime?

Topic

[don simon fbpe]

That’s about the best theory

That’s about the best theory that I have too, the chain was able to lock the rear wheel too. I’m sure when I get the chance to have a good look at the chain I’ll find tell tail signs. The lack of damage to the bike, from such a brutal stop is incredible. The last time I had such a sudden stop, the bike came out looking like this. https://www.flickr.com/photos/think180/3217751246/in/album-72157600206274323/

I’m surprised that the force this time didn’t snap the chain or mech hanger, didn’t take chunks out of the frame or bend the front mech.

Diagnosis is a broken shoulder and back to hospital to see what’s up with the leg/groin.

Hopefully I can have a short ride in a couple of weeks. 🙂

[kil0ran]

Cranks locking up? Only in

Cranks locking up? Only in the context of the chain dropping off the outside of the big ring. I had this recently on my MTB. Had been in the big ring for a while, hadn’t made a shift and all of a sudden under heavy power the cranks locked, I lost control and had a half crash into some surprisingly comfy heather. Turned out that the chain had shifted outboard. Couldn’t work out how and still not sure but I also noticed that it had jumped off the top jockey wheel. Chain was jammed between the big ring and the mech cage and was resolved by back-pedalling the cranks just a quarter turn. After that it was fine to ride and everything worked well, even under the testing conditions of a lumpy MTB ride. Point is if it had been a full crash the partial drop could easily have resolved itself when the cranks hit the road. Obviously in this scenario it wouldn’t have locked the rear wheel but it might have felt that way and it’s certainly unsettling enough to make you lose balance and spit you off.

[don simon fbpe]

Simon E wrote:

don simon fbpe wrote:

I’m trying to get my head around the physics of a jamming freehub.

Me too. A freehub failure is more likely to that the pawls fail to engage so pedals spin freely without the wheel moving.

However, from what you’ve written you seem to have discounted external factors (jammed spokes, stuck chain) and the pedal jamming just prompted me to think of the hub. Very odd that there seem to be no obvious clues and it was subsequently rideable.

This is the bit that I find most perplexing.

I doesn’t appear that anyone has had such a spectacular failure where the bike remains undamaged either. Which would give some sort of solace. I would expect a broken mech hanger to be minimum damge for these symptoms.

I’ll try and get some pictures of if when I’m more mobile and flexible.

[don simon fbpe]

Peloton were singled out for

Peloton were singled out for being overpriced and having particularly shite adverts!

[don simon fbpe]

A cursory look at the chain,

A cursory look at the chain, looking for scratches and contact on the chain, would indicate that the chain is fine. I didn’t spin the cranks for a full look, but at the moment I’d say all fine.

I’ve had the ripped mech enough times to see damage a dodgy link can do. Again the jamming of the chain and the mech staying intact seems a bit odd.

[Simon E]

don simon fbpe wrote:

I’m trying to get my head around the physics of a jamming freehub.

Me too. A freehub failure is more likely to that the pawls fail to engage so pedals spin freely without the wheel moving.

However, from what you’ve written you seem to have discounted external factors (jammed spokes, stuck chain) and the pedal jamming just prompted me to think of the hub. Very odd that there seem to be no obvious clues and it was subsequently rideable.

[Seventyone]

Surely you don’t need peleton
Surely you don’t need peleton just any stationary bike

Hope you heal well and quickly

[Secret_squirrel]

Like everyone else I’m

Like everyone else I’m struggling for things that only would have caused it once and then everything is ok again.

just coz it’s not yet been mentioned check the plates on every chain link.  My nearest experience to what you describe is a chain plate flaring out and jamming the drive train and pretzeling the mech hanger.   Definitely didn’t manage even 1.5 meters after that happened though!

[don simon fbpe]

Experience of mech hangers

Experience of mech hangers going would have a moment of slackness on the pedals before locking up as the chain gets slack. Not the sudden stop that I experienced.

I’ve just had a look at the rear end and no outward signs of damage, or marks on the oil on the chain, that would indicate the chain jamming. Obviously it needs a proper going over.

The upside of lockdown and injury is that my next visit to Cressex is a long, long way away.

[wycombewheeler]

hawkinspeter wrote:

If the cranks locked up, that shouldn’t cause the rear wheel to lock up as well.

but the reverse is true, if the rear wheel locks, the cranks will no longer turn.

Definately sounds like something got stuck and stopped the wheel. I’d have a look for any damaged spokes, and also any sign of damage to the back of the seat stays and top of the chain stays.

Sounds a lot like when my mech hanger broke, and the rear mech tangles with the wheel and frame, locking up the wheel instantly when I had been doing 30kmh. Just a big straight line skid for me, no crash, but broken bike meant I had to finish on foot.

In the absense of any sign of foregin object intereference, I would then be looking at the bearings, but as you rode home afterwards, that seems less likely

[don simon fbpe]

AlsoSomniloquism wrote:

I managed to get a 20mil wide, 150mil long bolt picked up by my back tyre and clonk the stays before I could stop. I wasn’t going fast and was scanning but just didn’t see it. However it didn’t cause a jam, only a puncture as the threads pierced the tyre. 

Whatever did happen probably got shook “loose’ with the resulting crash so unfortunately I don’t think you will get to the bottom of this. 

You’re probaly right. But it is an interesting exercise, imo. I won’t get a much clearer idea until I get a good look at the bike, which is a good couple of weeks away.

[don simon fbpe]

Furlough has been brilliant,

Furlough has been brilliant, the return to work had been getting in the way of riding prior to the accident.

I recently built up the rear end of one of the other bikes (Felt with Shimano) and didn’t tighten up the lockring, the only problem was indexing and gear selection were a nightmare. The ease that that mech hanger (on the Felt) broke surprised me, which is why I’m equally surprised that this mech hanger (on the Kuota) didn’t break.

No disc brakes.

[AlsoSomniloquism]

I managed to get a 20mil wide

I managed to get a 20mil wide, 150mil long bolt picked up by my back tyre and clonk the stays before I could stop. I wasn’t going fast and was scanning but just didn’t see it. However it didn’t cause a jam, only a puncture as the threads pierced the tyre. 

Whatever did happen probably got shook “loose’ with the resulting crash so unfortunately I don’t think you will get to the bottom of this. 

[don simon fbpe]

Cheers.

Cheers.

I’m trying to get my head around the physics of a jamming freehub. It would jam to the wheel, which would continue turning, no? It would become a fixed wheel and force me to pedal. Or, if the freehub broke loose, I’d continue pedalling with no drive, no?

[don simon fbpe]

Possible, but I don’t recall

Possible, but I don’t recall seeing anything on the path to obstruct, nor anything odd when I picked myself up. But entirely possible, cheers.

[Author]

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