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When I turn my pedals/ cranks the other way, my cassette keeps locking up causing my chain to slacken and I don’t know what’s wrong with it?

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    We need more information: What kind of bike is this? Single speed, derailleur bike, internal hub gear, e-bike, ... ?
    – Carel
    May 18, 2021 at 20:23
  • Also, is this true if you've just been spinning the pedals forwards (by riding it or by hand)?
    – Chris H
    May 18, 2021 at 20:29
  • It’s a 11 speed dh gears (shimano saint) it that helps and it just seems it keeps jamming if I turn the cassette anti-clockwise May 19, 2021 at 21:14
  • Not to be a pedant, but you probably mean that the freehub is locking up. The cassette by itself can't lock up, since it doesn't have moving parts. It may help to clarify: is the freehub locking up fully, or is there just a lot of drag? I suspect the latter; if the freehub were to lock up on backpedaling, then I assume you couldn't coast either.
    – Weiwen Ng
    May 20, 2021 at 14:54

1 Answer 1

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Edit: Assuming a standard bike, but take clues for internal gears or ebikes.

The rear derailleur keeps tension on the chain when you pedal backwards via a spring on the two jockey wheels. If there is resistance that exceeds the force this spring exerts then the jockey wheels will shift forward, slackening the chain, instead of the system working smoothly.

This can happen from a number of causes:

  1. Your jockey wheels have a ton of crud in them and need cleaning. This is the most likely cause, particularly if you don't take good care of your chain. Have a good look at them, and try to spin them by hand if you can get the chain off easily.
  2. Your freehub is blocked up somewhere. Try spinning it backwards while holding the chain clear with your other hand. If it doesn't spin smoothly then you need to take it to your LBS to have it cleaned/greased/fixed.
  3. Your bearings on the jockey wheels are shot. Sort of the same as #1, but needs a new part.
  4. Your chain is rubbing somewhere with a lot of friction. I'm guessing you'd notice this, but I thought I'd include it for completion.
  5. Something else is causing more friction than the derailleur spring can compensate for. You should be able to find it by looking at where the chain is stuck?

Hope that helps some!

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    6.: Badly adjusted gears which make it try to change gears when pedaling backwards (which of course does not work).
    – Michael
    May 20, 2021 at 9:07
  • If the freehub needs cleaning, on a number of newer hubs, the FH can be removed with a pair of 5mm Allen keys, or sometimes even without tools. The OP can consider doing that, wiping the pawls off, and adding fresh grease.
    – Weiwen Ng
    May 20, 2021 at 14:52

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