Rear Mech sounds like it;'s trying to change gear then slips

symo

Wasn't sure whether this is to be posted in the 'Strange Noises' thread. However, out on Sunday doing 60 miles around the area, when the mech felt like it was slipping in the larger sprockets. It sounded like it was the click when it was trying to change gear. The jockey wheels on the rear mech are in line with the cassette sprockets but it sounded like it wanted to change gear. A little later under load (stood up on steep hill) the chain did slip with a loud clunk causing me to slip down onto my seat.

Limit screws are correct, any suggestions. I am goign to change the chain which may or may not be an issue but does anyone have any other ideas what it could be?

Rear Mech is a Shimano Ultegra 6600.

ugo.santalucia

Well, if you want to run 10 speed setups, you'll have to live with the fact that occasionally they need to be re-indexed... if it wants to go down to the smaller sprocket, you need to add tension, by turning the mech screw anticlockwise... vice-versa in the opposite case

keef66

How many miles on the chain? Ditto the cassette? Is the indexing otherwise OK? ie the cable tension doesn't need tweaking?
Is there a lot of side to side play in both jockey wheels?
Have a close look at the chain to make sure there isn't a stiff link or it's about to part company.
Is the rear mech still firmly attached to the mech hanger, and is that in turn securely attached to the frame??

symo

Thanks both. I am looking at new jockey wheels, chain will be changed (probably done nearly 2000miles) did try tightening the thread. Going to go at it with the advice from the Park online guide.

Edit : Yes indexing appears OK when I have it up on the workstand, jockeys in line; probably is a chain issue. Will give it good clean anyhow.

g00se

Could be a failing freehub and the pawls are sticking/slipping. That could explain the big jump. Worth thinking about if it's not a warn chain or cassette.