Rear Cassette Cog/Sprocket is loose

faceplant77
faceplant77 Posts: 25
in MTB workshop & tech
I replaced my chain on the weekend and was cleaning my bike and noticed when fitting the new chain that the top Sprocket/Cog was loose and wobbly. I noticed that this was riveted, as I thought it was screwed in. Is there a way to replace this without purchasing a whole new derailleur. I'm not sure what type to get as it's a Deore Shadow Plus 10 speed.

Comments

  • JBA
    JBA Posts: 2,852
    edited August 2021
    Do you mean the upper jockey wheel?
    If so, it is held in place with a bolt so easy enough to replace.
    The bolt head for the bottom jockey wheel is on the outside of the cage but the upper one is on the inside of the cage.
    Bear in mind that upper jockey wheel will have some play in it as it acts as a guide.
    “Life has been unfaithful
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  • steve_sordy
    steve_sordy Posts: 2,454
    edited August 2021
    You have to buy them in pairs. Sometimes the top and bottom ones are different to each other. Sometimes you also have to have them the right way round. So pay attention to what is written on the jockey wheels themselves, the instructions that come with them are useful too.
    Google Shimano Jockey wheels 10-speed
  • reaperactual
    reaperactual Posts: 1,185
    edited August 2021
    I've just double checked my jockey wheels on an SLX derailleur. The top one is marked 'guide pulley', (some are marked centeron g-pulley) and the bottom says 'tension pulley' (or narrow depending on the derailleur model.)

    Like JBA says a few mm's of lateral float is perfectly normal to aid smooth shifting and fine tuning but there shouldn't be any sloppiness or twisting movement.
  • Ncovidius
    Ncovidius Posts: 229
    The upper jockey wheel is the ‘guide’ wheel, it has to have a bit of play in order for it to work properly. The lower jockey wheel is the ‘T’ ( for tension ) wheel, that one should have virtually no play, unless it’s worn out.
  • steve_sordy
    steve_sordy Posts: 2,454
    Do they look like these two?


    Or maybe the two on the left instead of the two new ones on the right?



    Then they are worn out and it's time to change. Jockey wheels can be badly worn and still function, but you will notice crisper shifting once you fit new ones. If the bearings are totally shot, then there is a risk that they will disintegrate on the trail, and leave you stranded. And you don't want that! :o

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