Chain comes of lower jockey wheel

roubaixtom

Hi,

I have a 105 5800 groupset on my winter bike and it does get a bit of a battering however it is well maintained

The chain has started to fall off the lower jockey wheel and catch between the cage and the jockey wheel. This then pulls the mech forward and makes a horrible noise

What could this be? Mech hanger? Bent rear mech? worn jockey wheels? There is a lot of play in the bottom jockey wheel, not sure if this would cause the problem.

Cheers

sungod

play could be a issue, or worn/damaged chain or wheel, or bent/damaged cage, or cage tension slack/sticky due to broken spring or bearing bunged up

Monty Dog

Also check frame rear mech hanger alignment which is more likely than the mech itself being bent - look at the bike from the rear to see if the mech cage is running in the same direction as the chain.

Bobbinogs

New jockey wheels are pretty cheap (no need to waste money on bling/bearings) and, IME, they don't get replaced as often as they should be. Whenever I do mine I am always amazed at how much better things run.

JesseD

The exact thing happened to mine recently which I reckon was down to a worn chain after months of use throughout the winter.

Picked up a cheap 105 rear mech as it was just as cheap as buying new jockey wheels!

Not chucked it on yet, but the difference in play in the jockey wheels between the old and new mech is significant.

keef66

"Picked up a cheap 105 rear mech as it was just as cheap as buying new jockey wheels!"

That's what I did when I rounded the hex sockets in both jockey wheel mounting bolts of my 105 rear mech. Bonkers to try to rescue it when it was 7 years old and a whole new mech was only a couple of quid dearer.

clickrumble

Same thing was happening to mine recently. Bought a derailleur hanger alignment tool and found the hanger was badly bent, straightened it out and it's fine now.