Urgent help needed on Dura Ace 7700 ss Derailleur

AssOs
AssOs Posts: 72
edited January 2009 in Workshop
Got first offer on a Dura ace 7700 ss short cage rear derailleur.

Need to know if this work with a shimano 6650 compact double chainset?

What problems might i get using a short cage derailleur with a compct chainset?

Thanks in advance.

Comments

  • softlad
    softlad Posts: 3,513
    I wouldn't have thought you would get any problems at all. I use a short cage Ultegra mech with a compact FSA chainset - there is not reason why it should not work...
  • SB75
    SB75 Posts: 10
    Just looked at the new 7900 rear mech. The important dimension is the distance between the jockey wheels. This hasn't changed to the best of my knowledge and Shimano quote a total capacity of 33 teeth. If your typical compact c/set is 34/50T (16T difference) you cou could run a 12-27T cassette no problem. Go for it.
  • AssOs
    AssOs Posts: 72
    i can't see myself why it wouldn't work but did manage to dig up some info.

    Not sure exactly what it means.

    total capacity-26 teeth or less

    Largest sprocket-27t

    smallest sprocket-11t

    front chainwheel tooth difference-14 teeth or less.

    My front chainring is 50/34 and cassette is 12/25.
  • SB75
    SB75 Posts: 10
    Based on the info given, that's not a suitable rear mech. Total capacity is the difference in the number of teeth between your largest and smallest sprockets PLUS the difference in number of teeth between your largest and smallest chainwheel. If you intend sticking with your current gearing then you need a mech with a 29T total capacity.

    That said, the capacity stated means that the mech has a long enough cage to take up the slack when changing between the extreme gears, ie. large sprocket/large chainwheel to small sprocket/small chainwheel. In practice you shouldn't use these gears anyway. If this was me, I'd be prepared to take a chance and wouldn't be put off from buying. But....it's your money not mine. You could, of course, eliminate the risk by buying the long/medium cage version if you can find one.
  • John.T
    John.T Posts: 3,698
    I am using a 2000 Ultegra 9sp mech on 50/34 and 12/27 with no problems. I think the 7700 is the basically the same. You should be OK with your set up. Just run the chain as long as possible for good changing.
    My Fleet.
  • AssOs
    AssOs Posts: 72
    thanks, You've put my mind at ease.

    going to pick up the mech tomorrow. It's brand new so can't return it once been fitted.
  • maddog 2
    maddog 2 Posts: 8,114
    I run a 12-27 with a compact and short cage Ultegra. No probs.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer

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