Austinite

I've got the Deore XT rear derailler on my new Long Haul Trucker and was adjusting it after some initial riding. What's the rubber sleeve on the top part of the tensioner? It seems to be wrapped around the front part of where the chain tensioner cage attaches to the rest of it. I can't imagine it's purpose except to maybe keep dirt from flying directly into that pivot point?

wesmamyke

It's a noise reducer/silencer if I understand what part you mean. On a MTB it will tend to slap the underside of the dropout, especially on some full suspension bikes. It was common to add a piece of rubber there before Shimano starting putting that thing on the MTB derailleurs.

electrik

SRAM showed shimano up - their rear mechs didn't slap the chainstay - shimano put rubber boots on to silence the problem. The new shimano shadow stuff doesn't have that issue and the rubber problem solver is gone.

Austinite

Watching that video I can't imagine how that can happen on a no-suspension bike like my Long Haul Trucker. Is the derailler slapping the chainstay due to the frame moving (suspension)? If it's unnecessary on my bike, I'm taking it off.

electrik

No, it is slapping the chainstay due to bumps, the FS makes it worse. I would leave it on, what would be the point in taking it off?