Crashed due to chain/derailleur fault.

[little dilbert]

I was cycling up an incline and was pedalling in a standing position, the next thing I know I have lost control of the bike and the ground is approaching.

All I can recall is that the loss of control resulted from a lack of resistance when pedalling which means the chain was derailed unintentionally and was not engaged on a cog. The thing that worries me is that I was cycling on the road when it happened and crashed onto the pavement, I could have also crashed into the road and into the path of a vehicle.

I recall a similar thing happening on a previous bike and I need to make sure that this doesn't happen in future. Both derailleurs are made by 'Simplex' on a Peugeot road bike. What is the recommended action to take? I don't feel the bike is safe to use in it's current condition.

 

[CopperCyclist]

Did you try to change gear? Changing gear when putting a lot of torque through the pedals is never a good plan. Whilst the chain shouldn't come off when pedalling if set up correctly, it may help you if you try to pedal faster, not harder. Instead of standing up and grinding away, exerting a lot of force through the chain try dropping down some gears and spinning the pedals faster.

 

[black'n'yellow]

downtube shifters..? Did you knock the left lever with your knee whilst out of the saddle? In which case, the 'recommended action' is not to do it again...

 

[HovR]

Alternatively friction shifters setup without enough friction will often shift into a higher gear by themselves when really putting a lot of power through the drivechain.

 

[little dilbert]

Did you try to change gear? Changing gear when putting a lot of torque through the pedals is never a good plan. Whilst the chain shouldn't come off when pedalling if set up correctly, it may help you if you try to pedal faster, not harder. Instead of standing up and grinding away, exerting a lot of force through the chain try dropping down some gears and spinning the pedals faster.

Nope I wasn't trying to change gear, it just came off by itself.

 

[little dilbert]

downtube shifters..? Did you knock the left lever with your knee whilst out of the saddle? In which case, the 'recommended action' is not to do it again...

I would agree with you if that was the case.. The lever is well clear of my knees in all positions.

 

[black'n'yellow]

I would agree with you if that was the case.. The lever is well clear of my knees in all positions.

Perhaps you could tell us what actually happened then? Where did the chain unship - front or rear..?

 

[marzjennings]

If the chain slipped, either up or down gear, or just slipped around the cog there would have been some resistance as the chain caught, slipped and caught again.

If you really felt there was no resistance, not even the chug-chug-chug of a slipping chain trying to find purchase on teeth, then I'd take a look at your freehub to make sure the pawls are engaging correctly.

 

[little dilbert]

If the chain slipped, either up or down gear, or just slipped around the cog there would have been some resistance as the chain caught, slipped and caught again.

If you really felt there was no resistance, not even the chug-chug-chug of a slipping chain trying to find purchase on teeth, then I'd take a look at your freehub to make sure the pawls are engaging correctly.

This may be the case. There have been occasions where I have been riding on this bike where the chain does not drive the wheel, it simply turns without resistance. I assumed that the chain was derailled but I can't be certain, it could certainly be possible the chain is turning the freehub without engaging the pawls as I did not think about this.

 

[black'n'yellow]

so did the chain come off or not..?

 

[monkeylc]

Anyway,,,,,

Are you ok mate?

 

[monkeylc]

Poor blokes come off his bike and all he gets is "Did the chain come off front/back,the back first/rear first?"
Yes i know that wasn't said I'm being sarcastic

 

[little dilbert]

Anyway,,,,,

Are you ok mate?

Could have been worse thankfully. Got off with a cut knee, grazed elbow and crushed fingers.

 

[HovR]

I assumed that the chain was derailled but I can't be certain, it could certainly be possible the chain is turning the freehub without engaging the pawls as I did not think about this.

Note that if this is an older/retro road bike, as it sounds like it is (with Simplex gears) it will be a freewheel, not a freehub (unless you have upgraded to a modern wheelset). Whilst it is possible to service a freewheel you will inevitably end up loosing bearings which you'll have to buy replacements for, so it may be cheaper just to buy a new freewheel.

 

[Milo]

Worn chain rings can do this IME.