at a certain point the chain will unship off the lower jockey wheel and run along between the jockey wheel and the side of the RM cage
Cassette - 6 months old
Chain - New and changed at 0.75-0.1 each time (Correct chain direction)
RM - 6 months old, jockey wheels correct direction
Gears - Indexed fine
Its done it before and I had to swap the RM to sort, that time I put it down to a bent RM arm, although I never remembered bashing it and thought it may have bent while left on its side in the back of the car. This time it's not been bashed or near the car for weeks and it's started again quite suddenly.
Any ideas?
chain too long ?
bent hanger ?
you're riding a DH course ?
Tried squeezing the cage plates in?
Mine did that in the last few km of a road race couple of weeks ago. Ripped the rear wheel out the drop outs at 25mph, managed to wrestle it to halt.
Changed the derailleur and everything was shifting fine again, got a new hanger on order too as it still doesn't look quite right.
Everything running perfectly up until it happened, no idea what caused it so decided best off changing both hanger and derailleur as I really don't want to risk that happening again!
Edit - 6800 by the way, but same principle?
Mine did this fresh out of the box when I was setting it up in the stand. I bent it slightly by hand and 3000 miles later it's still running smooth.
Thanks all, I tried to bend the last one when it happened and it didn't really have any effect.
It's hard to say if the RM's never taken a knock but I ran Tiagra for about 8 years before going for the new 105 and it's never happened before. Realise the tolerances are a bit tighter on the 5800.
Chain was measured off the old one before putting back on and corrected to be shorter by a link or so.
New RM I spose....
I had a Dura Ace 7800 mech do that. Once it happened it seemed quite keen to do it again. Replaced mech in the end.