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  • Oval chairing and oneup expander problem
  • cj95
    Free Member

    Hi
    Wonder if anyone has any suggestions?

    I put a oneup 42t Cassette expander on my bike with a radr cage on my rear derailleur and also an oval chairing on the front.

    My problem is I have now went through 2 rear derailleurs that have on (the lowest gear) caught on the cassette and snapped.

    Both times my bike has been tuned by a good mechanic and the gears have been shifting excellent on the flat. the bike seems great on the flat to the trail until I start climbing.

    The strange thing is that when I go to a slight uphill is when the lowest gear catches and breaks the rear derailleur.

    All the drive train parts are practically new and the chain length seems to be an OK length?

    My bikes a nukeproof mega 2012

    Thanks in advance.

    legend
    Free Member

    Chain long enough? B-tension screw wound in far enough?

    Northwind
    Full Member

    They might not have taken into account chain growth- no idea how much or how little your mega has mind. The best thing to do is remove the shock (or undo the bolts at one end and swing it away) and cycle the bike through its full travel in the tightest gear, and see what happens.

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    chrishc777
    Free Member

    I had this problem, after 2 mechs I worked out it was b tension. Just because it’s shifting well doesn’t mean you have enough, sometimes it’ll still catch

    cj95
    Free Member

    Thinking it may be chain length possibly then as there is a extended b tension screw that is out pretty far.

    Thanks guys

    dirksdiggler
    Free Member

    B tension out pretty far.. or in pretty far? it should be righty tighty in to help it clear the 42T, although the radr alleviates regular cage issues.
    any chance of posting a pic of your cage position in the largest sprocket?
    google suggests that the mega frames have lots of chain growth.. so even just sagged (slightly more sag when going up hill with weight distribution) could push the rear mech cage past its limit.

Viewing 6 posts - 1 through 6 (of 6 total)

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