Catastrophic drivetrain failure

[Scoosh]

The only time my rear wheel totally locked up was when I had been doing something to the freewheel (I can't now remember what nor why ) and, 50metres into a 150km audax, going up a hill to some traffic lights, the rear wheel seized up solid. Safe enough but no Completed that day ... and my riding buddy didn't notice I wasnae there for another 20 mins ...

Oh - and the other time was very recently, when I had been adjusting the boom length on my 'bent and hadn't lengthened the chain sufficiently and the rear derailleur needed adjusting ... and the derailleur ended up amongst the spokes ... once again, in a safe place and at slow speed and no long-term damage nor short-term cost

My luck should be due to run out soon, though ...

 

[snailracer]

Those little plastic discs that go behind the cassette do work, even if they do not look cool...

In this case, the plastic "dork disc" probably would not have helped. Note that the chain is not jammed between the largest cog and the spokes, which is the only situation where the plastic disc would have come into play.

What likely happened here is chainsuck - the low-tension run of chain nearest to the ground failed to release from the chainwheel and got dragged around, effectively shortening the chain and bending the derailleur so it got caught up in the spokes of the rear wheel. An extremely large plastic disc may have helped here (as used to be standard on some Decathlon bikes IIRC) but most discs tend to be the smaller types that only protect against bad limit screw adjustment on the rear mech.

 

[benb]

In this case, the plastic "dork disc" probably would not have helped. Note that the chain is not jammed between the largest cog and the spokes, which is the only situation where the plastic disc would have come into play.

What likely happened here is chainsuck - the low-tension run of chain nearest to the ground failed to release from the chainwheel and got dragged around, effectively shortening the chain and bending the derailleur so it got caught up in the spokes of the rear wheel. An extremely large plastic disc may have helped here (as used to be standard on some Decathlon bikes IIRC) but most discs tend to be the smaller types that only protect against bad limit screw adjustment on the rear mech.

Yep; I wasn't in the lowest (largest cog) gear, so it wasn't the case that the chain slipped off the largest cog into the cogs.
Still can't work out whether I could have done anything to prevent it - I'm reasonably good at keeping the chain clean and lubricated.

 

[snailracer]

Yep; I wasn't in the lowest (largest cog) gear, so it wasn't the case that the chain slipped off the largest cog into the cogs.
Still can't work out whether I could have done anything to prevent it - I'm reasonably good at keeping the chain clean and lubricated.

http://www.fagan.co.za/Bikes/Csuck/

 

[Moodyman]

Regular maintenance is a good way to spot potential problems but you say the chain was recently installed so you would not be expecting this.

I think the click per chain rotation should have been a clue. I hate creaks / noises and will stop to check things. I once had the click you describe and spotted a broken chain link plate on one side. I rode in a very low gear and spun in low cadence to minimise torque for the remaining mile into work. I then removed the offending link at lunchtime for the homeward commute.

 

[benb]

Regular maintenance is a good way to spot potential problems but you say the chain was recently installed so you would not be expecting this.

I think the click per chain rotation should have been a clue. I hate creaks / noises and will stop to check things. I once had the click you describe and spotted a broken chain link plate on one side. I rode in a very low gear and spun in low cadence to minimise torque for the remaining mile into work. I then removed the offending link at lunchtime for the homeward commute.

That's probably what it was. You just don't expect a click to suddenly deteriorate into something like this!

 

[Herzog]

That's probably what it was. You just don't expect a click to suddenly deteriorate into something like this!

You're right. It would have been nice if the click had turned into a bonk, and then failed.

 

[Pale Rider]

Ouch.
Same thing happened to me on a SMRbtH from Brighton.
Caused by my saddle pack bursting open and shedding my Montane jacket into the gears.
I had just turned off a dual carraige way doing about 30mph when it happened.
Jacket wrapped around the cassette and tore the deraiileur in half and twisted the chain.
Not a happy bunny.

Tried to single speed it but no good.
Luckily there was an Evans close by who took the bike in there and then. Supplied and fitted a new derailleur, chain and cable within half an hour.

Luckily the gears didn't shred your credit card as well.

 

[GrumpyGregry]

Out of interest ben what brand was that chain?

I'm hoping it isn't a connex/wippermann

 

[benb]

Out of interest ben what brand was that chain?

I'm hoping it isn't a connex/wippermann

KMC I think.

 

[SportMonkey]

I've had this happen before changing gears mid range. You probably took a knock and weakened the hanger an age ago and it's been slowly dying. You'll need at least a new cage too.

 

[potsy]

I've had this happen before changing gears mid range. You probably took a knock and weakened the hanger an age ago and it's been slowly dying. You'll need at least a new cage too.

Seem to remember Ben coming off a while ago, is this the same bike?

When mine went on our ride it wasn't for a few miles after the off iirc

 

[SportMonkey]

Seem to remember Ben coming off a while ago, is this the same bike?

When mine went on our ride it wasn't for a few miles after the off iirc

I forgot about that, it didn't even look like your bike was damaged, then pop.

 

[screenman]

The plastic disc stops your mech from getting mixed up with the spokes and causing the sort of damage you see here.

 

[Hip Priest]

At least you're in one piece! My catastrophic drivetrain failure led to a broken bike, a broken helmet and cracked ribs.