Pedals jam

[gordons]

Hi

I have a Giant Cross City straight handle bike. Twice now the pedals have jammed. More detail, changing gear on the front derailleur seems to jam the whole front gear a pedal bit. Happened today again today after having the bike in for service. I came off the bike the first time.

The rear derailleur lower cage plate and pulley are right forward when this happens and the chain is loose.

Didn't think it was possible for the whole thing to jam has anyone had a similar problem or any ideas what may cause it?

[cyclerUK]

Difficult to diagnose the cause but I would start with a warn chain and/or chainrings.
I assume the gears have been O.K. and that there has not been any damage to the front derailleur?
Next time try pedaling backwards and see if it releases.

[JohnnyCO]

Take it back to that shop. Sounds like something is worn or a hooked tooth. Chain wear can grab onto a tooth and cause "chain suck". Check all the teeth on the front rings for any bent ones. Is the front derailleur aligned correctly? Proper chain length? Pedal the chain backwards and look for any stiff links.

[trevgbb]

The FD is probably not set up correctly, it is either too high or not inline with the teeth. It may of course be bent or damaged, but the shop should have spotted this.
It also helps if you do not snatch at the gear change, but move it slowly.