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I have a shimano altus rear derailleur that won't go into biggest cog for gear 1 - it is two out so in the gear 3 cog. Would it be the limit screws needing adjustment or other?

I have tried adjusting the higher and lower limot screws, but the derailleur doesn't seem to be moving in or out when adjusting. What could be causing this?

The jockey wheels are not aligned

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No. The limit screws should be set once then left alone. If you've fiddled the limit screws, then turn them back. Limit screws control the edges of range of the derailleur, and that's all.

Position the limit screws such that the cage+jockey wheels cannot go outside the line of the outermost cogs on your cassette. There are two screws that physically limit the travel of the derailleur. If labelled, the L is normally the LOW gear (easy, most teeth, nearest wheel) and H is the HIGH gear (hard, least teeth, most-outboard from centerline)

Set them by loosening the inner cable pinch bolt, and the derailleur will move to the outside, though chain may get in the way. Physically turn the screw until the jockey wheel is about in-line with the smallest cog. Leave it alone.

The other side is a little harder - you need to actuate the derailleur by pushing on it and not chomping a digit in the moving parts.
In the Low gear, limit should be set just outboard of in-line with the largest cog. It is bad if the chain jumps over the top of your cassette and down the back. Ideally the chain should just make it there and no more. A little clatter here is okay.

Some minor tweaking of limit screws may be needed later in the process, but probably no more than a 1/4 turn total.

When they are set right, you'll never need to touch them again unless changing components.


The derailleur is only actuated by moving the shifter. My method for getting it in the ball-park is to get the bike in a stand or off the ground, then

  1. Loosen the pinch bolt that holds the inner cable into the rear derailleur
  2. Set the limit screws (described above)
  3. Set the fine barrel adjusters to about 1/3 of the way out. That means not tight and not falling out.
  4. Check all the ferrules are seated in the frame firmly
  5. Put the chain on second smallest cog, set the shifter on the hardest gear setting (slackest cable), and then pull through all the loose inner cable though the pinch bolt and secure it down.

This should be about right, but you then use the barrel adjuster to fine-tune things. Tightening the adjuster will effectively shorten the outer housing allowing more inner cable which moves the derailleur to the right, or harder gears.

Conversely backing out the adjuster effectively lengthens the outer housing, putting more tension on the inner cable and moving it toward the easier gears.

Many bikes work perfectly in some gears but have a slight chatter in others, more-so when on the workstand. Simply shift up and down the cassette while slowly hand-pedalling, looking for a sweet-spot.

This kind of thing is fiddly and dirty, don't get put-off.

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  • Thank ever so much for your reply. I will give this a go May 8, 2022 at 21:16
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    why do you put the chain on the second smallest? If i were to guess, i'd assume you are compensating for cable slackness or such?
    – Burki
    May 9, 2022 at 6:03
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    @Burki yeah - its a rule-of-thumb, by the time you've clamped the inner cable, there will be about the right amount of slack to drop the chain into the smallest gear perfectly, and only minor tweaks needed. There may be a machine that can pull the inner cable tight in the current gear, but by hand this heuristic gets you pretty close (which is why you preset the barrel adjuster to 1/3 out, giving room to move 1/3 in either direction and still have at least 1/3 of the threads engaged.)
    – Criggie
    May 9, 2022 at 6:15
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    @VaishalPatel the barrel adjuster for fine-tuning. I think you want to back it out (ie unthread it) a little. If you run out of adjustment, then screw it in and pull some inner cable through the pinch bolt (which is a coarse adjust)
    – Criggie
    May 10, 2022 at 21:27
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    Thanks, did manage to sort it. Next to tackle front gears May 12, 2022 at 16:05

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