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rear mech finer details

dieselgeezerdieselgeezer Posts: 231
edited March 2011 in Workshop
Have recently had some issues with Shimano rear mech performance. Have now got it to work almost OK but have 2 questions:-
1. What is the optmal length for the outer cable casing adjacent to the rear mech? I know too short means too tight a bend in the casing & too long would look ridiculous.
2. I've tried adjusting the b screw on the rear mech as per Shimano instructions but it doesn't seem to be doing anything obvious. Any simple instructions?
Many thanks
-- "I am but a spoke in the wheel of life" -- Ghandi


  • nicklousenicklouse Posts: 50,675 Lives Here
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Thanks nicklouse, I do like a clear cut reply. Re the b screw, I think my issue is the rear mech needs some freeing up (due to age) so that it accepts the "new" position called for when the screw is adjusted.
    -- "I am but a spoke in the wheel of life" -- Ghandi
  • onbike 1939onbike 1939 Posts: 708
    To free-up the RD, lube all pivot points then, with the chain on the large ring in front and the smallest sprocket on the rear, grasp the RD gear cable and, while turning the pedals pull the cable away from the frame. The RD should then move across the whole of its arc from small rear to large sprocket. Do this until you are sure the RD is moving freely.
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