chain jumps off front chainring

[squeakywheel]

I lost traction yesterday on ice going up a hill. There was a sudden and quick half rotation of the cranks. Then the chain was not on the front chainring anymore. I believe the chain jumping was a result of the loss of traction, but I'm not sure. The bike has a rear derailleur.

Is it common for the chain to jump when traction is lost?

[buzzman]

I lost traction yesterday on ice going up a hill. There was a sudden and quick half rotation of the cranks. Then the chain was not on the front chainring anymore. I believe the chain jumping was a result of the loss of traction, but I'm not sure. The bike has a rear derailleur.

Is it common for the chain to jump when traction is lost?

Need more info to accurately diagnose but are you saying the bike has a rear derailleur but a single chainring and no front derailleur? Is this the first and only time this has happened?

The loss of chain could be due to several factors from poorly adjusted cables, derailleur adjustment screws or a bent derailleur from recent falls or the bike being dropped. If you can rule out adjustment problems and it happens again when the bike is under strain:

It's more than likely it is not the loss of traction which caused the chain to drop off but the extra strain the bike was under while climbing in the icy conditions. If the bike has only a single chainring (or you tend to ride only one of the rings) on the front and a 7-9 speed rear freewheel your front chainring may need to be replaced. The drastic angle between the small rear cog and large rear cog with the single front chainring eventually wears down the teeth of the chainring and a symptom of that is it will begin by hopping off under circumstances like you just described. Look at your chainring and compare the teeth to a newer chainring and if they are worn down to sharp points- it could be the culprit. If you haven't replaced your chain and freewheel for a while now would be a good time for that, too.

[squeakywheel]

I don't have much experience on this bike. I bought it a few weeks ago. It appears to have not been riden much so I don't think wear is an issue. I see minimal signs of wear on the front chainring.

I removed the front deraileur and only have a chainring in the middle position of the crank. It is a 44 tooth chainring intended for use with a derailleur. It has 8 speeds in the rear. The front chainring lines up with the 4th gear in the rear. I was using the lowest gear when this happened. It has only happenned once. I could feel the wheel start to loose traction before it suddenly broke loose. I put my feet down. When I went to continue riding, I noticed the chain was off the front chainring.

[buzzman]

If it keeps happening recheck derailleur adjustments. You can also drop the chain off the front chain ring and looking at the ring from above and see if it's bent when you spin it.

If it doesn't happen again it's probably just an anomaly.

[2_i]

I removed the front deraileur and only have a chainring in the middle position of the crank. It is a 44 tooth chainring intended for use with a derailleur.

Mistake! The front derailleur cage prevents the chain from jumping in a drivetrain arrangement where the chain tension can change, as when riding with a rear derailleur. Put the front derailleur back, even if you want to ride with one chainring. Immobilize the derailleur's cage position by adjusting the L and H screws. Otherwise, your chain will jump quite regularly.