I have a hybrid bike, which, when I am sat on the bike, shifts and remains into the largest cog on the rear cassette with no problems.

However, if I take my weight off the bike, then when I start pedalling again, the chain skips between the largest and second largest cog until it settles back on the largest cog. Also, it is impossible to get it to shift into the largest cog when the bike is upside down.

I've tried loosening the L screw, but it hasn't worked yet. I'm guessing that if I keep loosening it it will eventually work, but the fact that the adjustment is so dependent on the load on the bike is making me think that something else might be wrong. Is there anything to worry about out or should I just go ahead and keep loosening the L screw?

  • If you back off the lower limit screw too far, you'll either overshoot the largest sprocket, or end up with your derailleur cage pinging-on then catching-onto spokes. Wither could be a ride-ending experience.
    – Criggie
    Sep 13 '16 at 9:08
  • Clarification: When you say its load-dependent, do you mean it gets worse when you stand on the pedals which puts more pressure on the pedals? Have you checked your chain and sprockets for wear? Skipping under load may be a symptom of wear.
    – Criggie
    Sep 13 '16 at 9:10
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    @Criggie No, it's other way around. It is fine under load. The issue is when setting off after stopping at lights or setting off for the first time, because the load was temporarily removed, it starts skipping for a bit
    – texasflood
    Sep 13 '16 at 9:18
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    As far as I remember it works fine on a climb
    – texasflood
    Sep 13 '16 at 21:50
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    It sounds to me like the frame is flexing and that affects the cable adjustment. It's possible that the frame is cracked, or that the cable is somehow misrouted such that frame flex affects it excessively. Sep 13 '16 at 22:15

Before you go any further, you should check (or have it checked at your LBS) your derailleur hanger. Oftentimes when the RD acts up and won't "tune", it has a poor reference point to start from. The derailleur hanger is easily bent out of alignment,and can render the rear an unreliable little beast. Double-check for any side-play in the crank, to see if that isn't a contributing factor, and get that hanger looked at. Good luck.

  • 1
    Also the derailer hanger mounting hardware. Sep 13 '16 at 15:45
  • True. I've seen one actually cross-threaded. God knows how he did it.
    – MikeW
    Sep 15 '16 at 13:29

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