You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Strange problem occurred last week. The bottom bit of the xt rear mech side plate fell off, as it turns out the chain had been not running on the jockey wheel correctly, and had sawn through where the red line is below. Picked up a new plate for a few quid which is a relief, but I'm keen to avoid it happening again. Any ideas what might be wrong? I didn't notice it making a noise (until that bit snapped off, at which point it started making quite a lot of noise). The mech hanger bolts to the underside of the pinch bolt on the 12mm axle, so it can swivel in the vertical axis. I guess if it was a bit off the chain might not land on the jockey correctly?
I'd guess the chain is jumping off the lower jockeywheel. Probably more likely at the extremes of the cassette.
I've experienced something similar a while ago, tried a new jockey wheel and tried bending the cage a little but it didn't make much difference and I had to fit a new mech in the end.
Check at the start of a ride? Keep an eye on it is about the best I can offer, is the jockey wheel knackered?
**** me. How mechanically unsympathetic do you have to be to not hear metal sawing through metal?!
Or feel it for that matter.
Don't shimano mechs have different top and bottom jockey wheels, with the top one able to move a bit side to side? (I might be misremembering this...)
If so, and if someone had installed new jockey wheels the wrong way up then the bottom one might have enough play to rub the chain against the cage. And it'd do it when changing gear, so you wouldn't notice the noise.
Don’t shimano mechs have different top and bottom jockey wheels, with the top one able to move a bit side to side? (I might be misremembering this…)
That sounds possible - the jockey wheels themselves are in decent nick and feel smooth, but didn't check for lateral play. I guess previous owner could have swapped them at some point and also not realised there was a top and bottom.
**** me. How mechanically unsympathetic do you have to be to not hear metal sawing through metal?!
Or feel it for that matter.
I see what you're saying, and it's hard to recreate the problem now that bit has come off. I'd guess it only did it when in the 12t sprocket, which is generally when going quite quick. I usually pick up on weird creaks or noises so I was pretty surprised! The alu plate is really soft and thin so I'd guess it'd only need a short period of contact to wreck it.