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I've followed the Park Tools Rear Derailleur adjustment video exactly, step by step, because my bike was jumping gears after I reinstalled the rear wheel after changing the tube.

The bike however won't shift in the rear from the 2nd biggest to 1st biggest cog. All other gears shift smoothly with seemingly no issues. I have tightened the L screw all the way, then did quarter counter-clockwise turns, trying to shift each time, and the chain at first would not shift at all, but after the L-screw was more loose the chain would momentarily shift to the big cog then return to the previous gear. I repeated this process until the L-screw was completely loosened and it did not appear to help. I also tried working the L-screw in combination with small clockwise turns of the barrel adjuster which seems to have made no difference.

This is a brand new bike which I’ve owned less than a week. Is there a way to fix this?

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  • Just to clarify: Are you sure that it worked when you bought it, i.e., the rear derailleur is physically capable to shift to the smallest gear when everything is installed and adjusted properly? I'm asking because you may never have used the easiest gear after you bought it unless you went on a mountain tour. Commented Oct 14, 2022 at 10:39
  • Why does a new bike need a new wheel?
    – acidjunk
    Commented Oct 14, 2022 at 13:48
  • @Peter-ReinstateMonica sorry I didn't clarify this. yes, it was riding fine for a few rides before this issue happened.
    – Norse
    Commented Oct 14, 2022 at 15:10
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    @acidjunk sorry, should've specified, I changed the inner tube, not the tire
    – Norse
    Commented Oct 14, 2022 at 15:10
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    @Criggie No. I was finally able to resolve the issue by shifting to the 2nd biggest cog and loosening the barrel adjuster until it was able to shift to the 1st biggest cog.
    – Norse
    Commented Oct 15, 2022 at 16:32

1 Answer 1

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Absolutely it's fixable.

The L and H screw should never need to be touched normally - they act as stops to prevent the chain going too far and jumping off the cassette.

The cassette will end up in the same place on wheel reinstallation, and if not then something has changed. Check that the axle is firmly in the dropouts, and nothing's hanging up on brakes or mudguards. Also check if washers are on your axle and have ended up changing sides of the dropout.

As for getting your bike back in order

  • FIRST UP there are a lot of chompy moving parts that want to eat your fingers and clothes and hair, etc. Be mindful. Also don't get the wheel going too fast.

  • Try and get the back wheel off the ground. A workstand is nice, but rope or old inner tubes can be used to hang it up too.

  • Set your right-hand gear shifter into the hardest gear while slow-pedalling with your hand.

  • Adjust the H screw until the chain sits on the smallest cog while slow-hand pedalling.

  • Then do the same for the L screw, shifting to the "easiest" gear. Be careful not to jump the chain completely over the cassette, this can cause damage at speed.

  • Tweak the L limit screw until the chain is just making it up to the largest cog.

At this point the limit screws should be right, and never need touching again. Then move on to indexing.

  • Use your left hand to turn the black plastic barrel nut that is on the rear derailleur, around where the cable enters. Tightening will effectively shorten the outer housing and moves the chain toward the smallest/hardest cog.
    Likewise, backing out the barrel nut makes the outer longer essentially tightening the cable, like you're pulling on it with the shifter lever making it move toward the easier gear with the most teeth.

  • You can test by shifting with your right hand, and use your left hand on the right pedal. There may be some compromise between shifting once per click up compared to down. Some iterations will be needed too.


Finally, your last resort is that if all this sounds too hard, most bike shops offer a tweak-up service on bikes they sold. All new bikes have a setting-in period where the cables develop a set, and everything beds in. This may be free, check with the bike shop.

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    Note: If you have a lot of cable tension (i.e. the barrel adjuster too far out) or friction the derailleur might be unable to go to the smallest sprocket even with the H screw all the way out. Vice-versa for the biggest sprocket: If you don’t have enough cable tension to shift to the biggest sprocket loosening the L screw won’t help.
    – Michael
    Commented Oct 14, 2022 at 9:37
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    More for the questioner: a way to look at the H and L screws are as adjustable “guardrails.” Just like guardrails on a bridge prevent your car from driving off to your demise, the L and H screws set the High and Low gear “guardrails” to prevent derailleur movement beyond the edges of the cassette. These guardrails prevent you from driving your chain to its “demise,” either between the cassette and the frame or between the cassette and the spokes of the wheel. As @criggie said, once H and L are set, you “should” never need to adjust these ever again.
    – Ted Hohl
    Commented Oct 14, 2022 at 18:16
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    @TedHohl so theoretically if the H and L screws are properly set and I'm still having this issue in my original post is the answer to adjust the barrel adjuster? or could it be some other variable
    – Norse
    Commented Oct 15, 2022 at 0:30
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    @Norse, correct. One can even set the H and L limit screws without a shift cable attached. They literally are guardrails so the derailleur can only travel between them. If your cable is not way off, then your barrel adjuster can get the derailleur indexed correctly. If it is off too far, then it will require loosening the screw that clamps the cable to the derailleur and moving it so the barrel adjuster will be able to make the fine adjustment. If you have not loosened the cable bolt and the adjustment was not way off, you should be able to get things back with just screw adjustments. “IF.”
    – Ted Hohl
    Commented Oct 15, 2022 at 0:59

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