Chain sliping off lower jockey wheel.

keithc440

I have the following set up: Sram Force 10 speed 12-23 with 53/39.
The indexing seems spot on but I have a problem when on the 53 and the 17,18 or 19, that the chain will slip off the lower jockey wheel from the side facing away from the wheel (don't use the 21 or 23 with the 53). I had this problem start to develop a while ago and replaced the jockey wheels. This didn't seem to make much of a difference. The rougher the road surface the worst the problem. I still keep pedaling and it will slide back into place but not for long. The problem seems to be getting worst. On the 39 there is no problem at all. The bike shop said rear derailleur alignement is fine (might get them to check again). Could the chain be too long ?

tim_wand

Im a bit OCD about indexing. Checked out my ride today and it wouldn't change down to lowest gear on the back even when on the Granny ring.

Did the usual Hi and Lo screw adjustments after taking the slack out of the cable on the highest ring (No joy) and then when changing down into the highest gear on the block the chain started coming out of the cage on the bottom jockey wheel.

I then remembered the last ride out about a mile from home and in the big ring, my mate ran into the back of me, I managed to stay up right and came to a stop and thought at the time no damage done.

I was shocked that on getting on my drive my mate complained of his front wheel dragging and had in fact buckled his rim.

Still no apparent damage to my bike. It was only on checking the indexing this morning I found the Mech hanger was bent out of alignment very slightly.

This resulted in not only not being able to shift into the low gear of the block, but the chain coming out of the mech cage on the lower jockey wheel when in the highest cog on the back.

So I don't know if you ve had a blow to the mech hanger. But check its alignment.

I took mine out of the drop out and managed to straighten it up, now everything is fine.

You say however that the LBS says your mech alignment is fine.

sungod

if it's happening in the middle of the cassette i wouldn't think it was related to chain length

check that the cage isn't bent/twisted, and that the chain hasn't got any bent/stiff links

on sram red rear mechs the pivot that the cage rotates can get worn over time, this allows the cage to move off axis, so the effect is similar to a bent hanger, easiest way to check is remove the chain and manually rotate/wigglethe cage to see if there's slack on the pivot

keithc440

Thanks for the replies. Sungod I checked the pivot that the cage rotates on and it does seem slack. I take it that I will need a new rear mech. Will call into LBS on Saturday and see what they think.

lef

HAve a check to see if the inner side of the mech cage could have been installed upside down. Worth a check. At least on Shimano and Campag there is a little piece of metal bent over to help guide the chain. if this is on the wrong side the chain and indexing can misbehave.

keithc440

Inner side of mech cage installed correctly thanks. Just went to check.