Chain slipping BADLY after change

I've had the chain break a couple of times and each time, removed a link and carried on. A while back it went again and following the repair I felt the chain was now exceedingly short, so when I got home I replaced it with a new chain.
Next time I rode the bike, the chain was slipping whenever light pressure was applied - so riding on the flat in a middle gear meant it slipped about 2-4 times per revolution of the pedals, 1-2 times on each downward push.
Having tried a number of things to resolve this, I confess to defeat - I've replaced chains many times before on bikes and never had anything like this happen.
I'm wondering if the derailleur is damaged - the cogs on it seem to have a significant amount of movement, particularly the one closest to the cassette - also when I look at my other bike, the cog is very close to the cassette while here there's a noticeable distance, so I wonder if a spring is failing?

I attach a few images in the hope someone can spot something that doesn't look right.

Any suggestions welcome.






Comments

  • whyamihere
    whyamihere Posts: 7,713
    The derailleur looks a bit beaten up, but this problem is more likely to be caused by the cassette being worn. That can be seen in this picture: https://ibb.co/0qLqfn2 - Notice that the teeth on the middle and larger cogs are significantly sharper than on the small cogs. The old chain would have worn together with the cassette and developed enough slop that it didn't skip. The new one can't accommodate the wear.
  • david37
    david37 Posts: 1,313
    hello.

    From what I can see the cassette looks very worn and prob needs replacing

    The distance between the derailleur and the cassette is adjusted by the B screw on the Mech. Yours looks ok nothing to worry about but adjust if you want. On a road bike closer is generally better but again yours looks fine.

    its very hard to tell of course from a photo but your gear hanger / cage seem straight enough.

    it might be something as simple as adjusting the cable tension using the barrel adjuster on the mech. or you might need to replace your cassette.

  • Thanks for the input guys - a new cassette won't break the bank and this one has done a number of miles - would I need to replace the front cogs too or is it normal to just replace the cassette and chain?

  • whyamihere
    whyamihere Posts: 7,713
    It depends on the wear. Judging by the wear on the cassette, I'd guess that at least 1 chainring will be badly worn, but it's impossible to say without seeing pictures. Basically, if the teeth are obviously worn and sharp, they'll need replacing. If they look ok, give them a try. You can also post another picture here and people can look at them.
  • david37
    david37 Posts: 1,313
    whyamihere knows.if the chainring teeth are looking like shark fins, then it's def time for a change. you might also check and see none are missing / bent whilst you're at it.
  • The front is a bit of a mixed bag:
    https://ibb.co/1sXzh6w
    https://ibb.co/7p3rKDz

  • Any suggestions on how to pick replacements?

    The rear cassette is currently a Shimano 9 speed, 11-32T, The front is a square taper Shimano 22/32/42

    i can see a replacement front chainset here:
    https://www.tredz.co.uk/.Shimano-FC-M371-Square-Taper-Chainset_63608.htm

    For the cassette - I'm not particularly concerned about weight, so
    https://www.tredz.co.uk/.SRAM-PG970-9-Speed-MTB-Cassette_17941.htm
    would do - is it ok to mix and match Shimano with SRAM?

    I have some suspicions about the new chain I have - it's a basic Clarks 9-speed chain, so thinking of ordering this at the same time:
    https://www.tredz.co.uk/.Shimano-CN-HG53-9-Speed-Chain_77066.htm


  • whyamihere
    whyamihere Posts: 7,713
    edited March 2021
    That cassette and chain would work, but the chain you have is probably fine. The chainset doesn't necessarily need to be replaced. The inner and outer rings look serviceable, but the middle could do with replacing. Something like this should fit: https://www.sjscycles.co.uk/chainrings/32-shimano-deore-fcm510-104mm-bcd-4-arm-middle-chainring-32t/

    If you do want to change the chainset as a whole though, just check the BB axle length. The one you've linked to requires a 123mm BB, if the one you have doesn't match that, it could throw the chainline off and cause problems. Unless you wanted to replace the BB at the same time of course...
  • JBA
    JBA Posts: 2,852
    I'd say the middle ring is shot and needs replacing.
    Inner looks fine and the outer doesn't look too bad.
    Do what whyamihere suggests and just buy a middle ring (and a peg spanner to undo the chainring bolts).

    You won't have any problem with a SRAM cassette and your new chain is fine. If you do want to replace it though then I'd recommend a KMC X9 one. They last longer than Shimano chains and work really well.
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • If you’ve ridden with a chain that’s stretched to over 1% for any length of time, you’ll have knackered most of the sprockets in the cassette. The good old adage that you can’t teach and old cog new links is very much the case here.
  • The good old adage that you can’t teach and old cog new links is very much the case here.

    Haha - I love that - had never realised that regular chain replacement was so important, but then again, I've never ridden any bike for as hard and long as this one before..
  • steve_sordy
    steve_sordy Posts: 2,452
    edited March 2021


    ..........."you can’t teach an old cog new links".............

    Love it! :)