Rear derailleur help

taon24
taon24 Posts: 185
edited March 2015 in Workshop
When i shift into the largest sprocket (smallest gear) the shift cable seems to lose tension. This prevents shifting back to a smaller sprocket as there seems to be insufficient pull from the derailleur on the sti lever. Any ideas as to the cause of this? Indexing seems fine otherwise and i can go from smallest to largest sprocket. Running long cage 105 5700 10spd. Any fixing or investigating ideas?

Comments

  • arlowood
    arlowood Posts: 2,561
    Sounds very much like your inner cable is sticking at some point.

    Just to clarify - the default position for any derailleur is with the chain on the smallest sprocket. To change to a larger sprocket your STI is pulling the cable against the spring tension in the parallelogram of the derailleur. Once you release that tension to change from larger to smaller sprocket by flicking the inner paddle the spring should pull the chain over onto the next smallest sprocket.

    If that is not happening then it must be due to the inner cable fouling along its length or possibly in the STI itself.

    Either remove and check/lubricate the inner cable or buy some new cables and fit them.
  • trailflow
    trailflow Posts: 1,311
    Check the b-screw adjustment, is the top jockey wheel hitting the largest cog when in the lowest gear ?
  • davem399
    davem399 Posts: 269
    I recently had this on my 105 5700 setup. It was the inner cable frayed where it enters the STI lever. I found it by peeling back the rubber cover on the lever. Quite a common issue according to posts on the Internet.

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