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Accident post mortem.

by don simon fbpe
Sun, Sep 06, 2020 19:21
43

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?

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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43 comments

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don simon fbpe replied to wycombewheeler | 4 years ago
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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. mail

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kil0ran replied to don simon fbpe | 4 years ago
2 likes

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.

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don simon fbpe replied to kil0ran | 4 years ago
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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-7215760020627...

https://www.flickr.com/photos/think180/3216918939/in/album-7215760020627...

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. 1

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Sriracha | 4 years ago
1 like

Do you have mudguards? Possibly something wedged between the tyre and rear mudguard?

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don simon fbpe replied to Sriracha | 4 years ago
1 like

No mudguards on this bike, the severity of the stop would have ripped the tyre and broken the mudguard too. It was brutal. Good job I'm hard as nails! smiley Cheers.

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hawkinspeter | 4 years ago
1 like

Odd. Could it have been something like a stick getting between spokes and stays, though that would probably have made a bang. Otherwise, I'd be looking at chain and rear cassette, though whenever I've had a chain misbehave it's not rideable until it's freed.

Anyhow, glad it wasn't worse and get well soon.

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don simon fbpe replied to hawkinspeter | 4 years ago
1 like

Thanks for taking time out from what must be the busy nut collecting season! How are you?

I've checked the spokes as best I can, and no obvious damage. I can't get my head around it being the cassette or chain as getting caught between spockets, it'd still freewheel. And dropping off either side of the cassette would a) leave damage and probable rip off the mech and b) jam the chain, no?

The chain came off, and wasn't jammed anywhere.

The real pisser is that I'm about 300km short of 10,000 lockdown kms. Otherwise I'm all good, just a bit broken.

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hawkinspeter replied to don simon fbpe | 4 years ago
1 like

I'm doing good. Had fun being furloughed for a bit and am now "working" from home which suits me.

I had a rear wheel lockup when a cassette lockring was loosening up (I make sure they get properly tightened these days) and then got stuck on the frame, but again that required intervention to get the rear wheel moving again and it wasn't really sudden so it didn't cause an incident.

If you've got disc brakes, would it be possible for a small stone to get stuck between the caliper and the disc? I suppose that could lock up a rear wheel and "disappear" after throwing you off though I've never heard of it happening.

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don simon fbpe replied to hawkinspeter | 4 years ago
1 like

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.

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ktache | 4 years ago
1 like

Hope you make a quickish recovery.

Your ride home sounded impressive.

How old is the freehub, were you pedalling or freewheeling at the time?

I've had a couple of newer Shimano ones go by becoming fixed gear intermittantly.

I managed to ride home both times, but had to remember to pedal constantly, but they never became permanently fixed gear, would frehub for a bit, then not.

I have also had cup, cones and bearing rip themselves to peices, and a long time ago had a rear spindle break, they all cause the wheel to lock, but there is never riding on.

 

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don simon fbpe replied to ktache | 4 years ago
1 like

How are you dude?

Shoulder is the real bummer as I have rollers at home, so they're out of the question at the moment. I have seen those Peloton trainers that look quite good.... And the adverts make them look as if they'll improve my lifestyle...

I was pedalling, I'd just overtaken a couple of lads and was pulling away at about 30km/h.

It's Campagnolo, if that is relevant.

But even if it went fixed, it wouldn't have jammed, would it? I'd only have noticed when trying to freewheel, no?

I don't think it's bearings as a) I rode it for a further 1.5km afterwards without problems (the caveat here is that when the taxi arrived to take me home, I couldn't remember my address) and b) I've just given the wheel a wobble in the frame and all feels good.

It'll be interesting to give it a proper look over once my shoulder is out of the sling and I can get the bloody thing on a bench. yes

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Seventyone replied to don simon fbpe | 4 years ago
1 like

Surely you don't need peleton just any stationary bike

Hope you heal well and quickly

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don simon fbpe replied to Seventyone | 4 years ago
1 like

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

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