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I had to replace my front derailleur on my mtb. Now I just need to adjust it however the limit screws are not marked. Does anyone know if the L limit screw is closest to the frame? Or is that one the H limit screw?

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  • What derailleur do you have?
    – David D
    Dec 28, 2022 at 14:06

2 Answers 2

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It varies depending on design - there's no hard and fast rule.

A technique to try:
Let the mechanism relax under spring tension. This should let it move toward the bike's centerline, which is the "low" gears, aka the easier ones.

Then use a suitable tool to twist each limit screw a half-turn - maybe a JIS screwdriver, a flathead, a hex or torx driver). The easiest screw to turn will be the High limit screw, because nothing's pressing against it whereas the low screw is pressed on by the spring pushing the mech.

Confirm that by turning the other limit screw, and it should subtly move the derailleur cage. That's your low limit screw.


Same technique works for the rear mech, except that when its relaxed the mech is in the high/hardest gear on the rear.


For completeness - cery occasionally you may run into another kind of front derailleur which is "top-normal" and is essentially backward. These tend to only appear on old vintage bikes and are rare. In these, the spring pushes the mech toward the high gear (large chainring/ hard gear) and your shifter action pulls the mech toward the center, and smaller chainring(s)

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    Just one small detail: Your technique only works properly if the derailleur is actually limited by the Low limit screw. If both screws are easy to screw in you can just continue screwing them in until one of them starts engaging which will also tell you which is the High and Low screw.
    – Michael
    Dec 28, 2022 at 8:39
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Quite often it’s possible to see the tip of the screw and if it’s making contact. The one which is making contact (or almost making contact) is the one which is relevant for the current shift position.

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    This is a tried and true method (if you can see the screw in contact with the mechanism, and usually you can see it). It follows that you can move the derailleur a little bit (by hand or shifter) and see how the mechanism contacts the limit screws at each extreme. I know I have to reacquaint myself as to which extremes the H and L refers to (especially on the rear derailleur). Well said!
    – Ted Hohl
    Dec 28, 2022 at 21:16

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