Dura Ace 7800 rear mech problem

owenrwall Posts: 14
edited February 2009 in Workshop
I've recently fitted a DA 7800 SS rear mech to my winter bike (after converting it from Ultegra 9 to DA 10 speed). I'm fairly good with the bike set up etc, and only usually need the help of my LBS if I can't extract BBs etc.

The problem I have is after indexing the rear mech, I'm finding that it won't hold the chain firmly on the 25 rear sprocket without wanting to partly jump off onto the 23 sprocket. All the other sprockets index perfectly (on small & big rings). I've re-indexed it twice, and played around with the rear mech barrel adjuster but with no effect.

Now, the rear mech I've fitted was involved in a crash which destroyed the previous frame to which it was attached. My question is, can I further adjust the rear mech so it indexes to the 25 sprocket, or do you think it could be damaged, and if the latter, how do I tell ?


  • alfablue
    alfablue Posts: 8,497
    Sorry if I'm stating the obvious, but have you set the low limit screw correctly?
  • maddog 2
    maddog 2 Posts: 8,114
    what ab said.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • Doh :shock:

    That's the one thing I haven't fiddled with - what a berk i am - I'll get right on it and let you know!