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I have got a single speed bicycle (Pure Fix Original Series) and I need to remove the rear wheel to the replace the punctured tube. The rear dropout has adjustment screws (I am not sure if this is the right term but you can see them in the photo). enter image description here I have never removed the rear wheel of my bicycle since I bought it about a year and a half ago. I am not sure if I have to loosen the adjustment screws when I remove the rear wheel or if I have to readjust them when I put the wheel back. I would like to make sure that I do not mess something up when I remove and reinstall the wheel. So my questions are as follow.

  1. Do I have to loosen the adjustment screws when I remove the rear wheel?
  2. Do I have to readjust the adjustment screws when I put the wheel back having in mind that the adjustment was done about a year and a half ago? If yes, how should I do that?

Any help is much appreciated!

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With a backwards-opening (track) dropout like you have, yes, you typically will have to screw them out to get the slack you need to remove the wheel.

They achieve a couple different things on a backwards opening dropout:

  • On a similar dropout without them, you have to keep the centering of the wheel more eyeballed in place as you tighten the nuts, and as you do that you also have to keep the chain tensioned. There are some tricks to doing that without much hassle, but the adjustement screw(s) make it much easier. With them, starting from the point where they're loose and the wheel is in place, you tighten the drive side one down until you have the chain tension you want, tighten the drive side axle nut, and then screw the non-drive side one in until the wheel is centered in the frame and then tighten the nut.
  • They eliminate the wheel's ability to squirm around as you tighten the axle nut, which also helps with achieving the above.
  • They are an insurance policy against the hub being able to slip in the frame under heavy loads. Most of the time this shouldn't be a problem if the axle nuts are properly prepped and tight, and many frames have similar dropouts without adjusting screws.

One of the deals with them is as the drivetrain wears, your chain will pick up just a little slack, so it's likely they're not in proper adjustment per se anymore anyway if they've been in place for a year and a half.

This all leads to the question of how to use them properly to get correct chain tension on a fixed gear or singlespeed. That is a good question and there is a lot written about it. The simple answer is that as you add tension to a chain on a fixed/SS drivetrain, there reaches a point where the chain begins to bind a little as you spin the cranks because all the free space in the internal parts of the chain is being taken up. You want to be just shy of that point, but still tight enough that it's physically impossible for the chain to derail and that the top run of the chain looks like a straight line from the cog to the ring. As you read different takes on how to define good chain tension, it's pretty common to see people site numbers for how much the chain should be able to wiggle up and down, but these are inexact at best because it depends meaningfully on the chain construction, chainstay length, etc. Use your tensioning screws to go to where you can feel it binding a little, then back off from there. Also while messing with them, always put a bit of oil or grease on the threads if they feel dry.

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  • Thank you very much for such a thorough answer! It is very helpful. It is difficult to explain in words and I am not a native speaker, but could you please explain a bit further how I can find the spot where the chain begins to bind a little? What signs should I look for? Should I listen for some different sound?
    – Cm7F7Bb
    Jan 16 at 19:22
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    Many single speed bikes have a chain with a special link that is held by a U-shaped clip. Once you've opened the chain, you can remove and put back the wheel without touching the tension screws. Mind though, because the clip may easily be ejected at speed.
    – Carel
    Jan 16 at 21:09
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    @Cm7F7Bb Starting from a point where it's clearly loose, backpedal the bike with your hand, then add tension, then backpedal it again. Too tight is when you backpedal it and there begin to be spots where there is resistance. It happens in spots when you cross that transition zone because the parts aren't perfectly concentric. For most bikes, back it off until there are no tight spots. Sometimes a concentricity problem on the ring or cog forces you to accept some tightness in order for it not to be too loose elsewhere. The limiting factor with that is derailment should always be impossible. Jan 16 at 21:51
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    @Cm7F7Bb : FYI: There is another type of rear axle position adjustment screw that sits at the rear end of a track drop-out. Therefore it stays with the wheel and it removes the need for unscrewing and re-adjustment after you put the wheel back in
    – Carel
    Jan 18 at 13:10

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