Forum home› Road cycling forum› Workshop

SHIMANO 105 R7000 REAR DERAILLEUR SET UP

chris74chris74 Posts: 15
in Workshop
on my shimano 11-30 cassette when i pedal backwards the chain jumps on the 12t only.
the indexing on the other gears is ok and doesn't rattle.
is my derailleur hanger slightly bent?
the bike is a pinarello gan disc.

Posts

  • darkhairedlorddarkhairedlord Posts: 7,180
    Try pedalling forwards. That might help..
  • smethleysmethley Posts: 45
    Sounds normal to me.
  • ed1973ed1973 Posts: 284
    Bent hanger
    Sticky link in chain
    Bad chain line
    All a possibility
  • chris74chris74 Posts: 15
    Thanks I though the first two but the bike is only 7 months old
  • PMarkPMark Posts: 159
    I wouldn't have thought it was a bent hanger if you can change gears without issue. You could try adjusting the B tension screw on the rear derailleur. It could be the derailleur is a bit too far from the cassette.

    Otherwise I would look at changing the chain, then the cassette. (That is assuming it hasn't always done this).
  • chris74chris74 Posts: 15
    I have changed the cassette but not the chain and checked the b tension which is fine.
  • webboowebboo Posts: 6,057
    Does it jump when you pedal forwards.
  • chris74chris74 Posts: 15
    No it doesnt.
  • darkhairedlorddarkhairedlord Posts: 7,180
    is the no9 gear picking up the chain as you spin it backwards? I doubt if it is the RD as that should only affect things pedalling forwards. Are the chin and cassette clean and correctly lubricated? old lube can get a bit sticky. especially grease from the cassette instalation.
  • chris74chris74 Posts: 15
    If By no9 if you mean 13t sprocket this works perfectly. The chain was last cleaned about 2 weeks ago and the cassette is clean
  • darkhairedlorddarkhairedlord Posts: 7,180
    Yes, the 13t on your cassette. When it is in 12t and you pedal backwards, does the chain get snagged on the edge of the 13t?
  • chris74chris74 Posts: 15
    i dont think so as its that as its not rattling against the 13t, and if i loosen the tension on the rd cable it doesnt make any difference.
  • darkhairedlorddarkhairedlord Posts: 7,180
    Pop it on a work stand and observe as you rotate it backwards, then you should be ablecto see what is causing the chain to lift. It won't be the rd because you are pedalling backwards.... iscthis when in the big ring or small on the chainset?
  • chris74chris74 Posts: 15
    it's in the big ring. when i have it in the work stand it seems as though its one part of the chain that is lifting on the 12t cog.
  • andyrrandyrr Posts: 1,814
    chris74 said:

    I have changed the cassette but not the chain and checked the b tension which is fine.

    Normally chains are renewed 2/3 times over the life of a cassette before that requires renewal - a new cassette would mesh best with a pretty new chain.

  • webboowebboo Posts: 6,057
    chris74 said:

    No it doesnt.

    Then it’s not really an issue.
  • darkhairedlorddarkhairedlord Posts: 7,180
    Is it the jockey wheel teeth touching the cassette?
  • pilot_petepilot_pete Posts: 2,120
    chris74 said:

    Thanks I though the first two but the bike is only 7 months old

    Never assume. A hanger can look straight but be bent slightly even on a brand new bike. Although it doesn’t sound like the cause of the issue of the gears all change correctly.

    In my experience it will be the chain catching the next bigger cog teeth slightly. Could be a chain line issue (washer/ spacer fitted/ not fitted) on the crank axle. Worth a check. TBH it’s not really an issue if it doesn’t do it pedalling forwards.
  • akhakh Posts: 206
    The teeth aren't remotely symmetrical so I'm not surprised they don't work equally well in both directions.





  • MattFalleMattFalle Posts: 11,644
    akh said:

    The teeth aren't remotely symmetrical so I'm not surprised they don't work equally well in both directions.





    what you on about Willis?
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • oxomanoxoman Posts: 11,732
    The teeth have specially designed ramps for changing up and down gears, hence they're not symmetrical. TBH I cant understand why anyone would want to pedal backwards unless they had coaster brakes.
    Too many bikes according to Mrs O.
  • MattFalleMattFalle Posts: 11,644
    The chain should not fall off just by pedalling backwards.

    agree there is no real reason for pedalling backwards but the chain shouldn't fall off.
    .
    The camera down the willy isn't anything like as bad as it sounds.
  • akhakh Posts: 206
    The OP said "jumps", not quite sure what they mean by that. I didn't understand it to mean the chain completely comes off the 12 tooth sprocket.

    There is also the possibility the 12th tooth sprocket is simply more worn that the rest as the bike had been used.
  • chris74chris74 Posts: 15
    It's a new cassette so isnt worn.
  • chris74chris74 Posts: 15
    i do have fulcrum racing 3 wheels on as well but cant see this been the issue unless its the spacer on hub
  • vincesummerskRoxcBTrvincesummerskRoxcBTr Posts: 369
    Sounds like the chain is most likely suspect, have you tried it with a new chain? It is usually chain that wears first and some times strangely quickly.
  • darkhairedlorddarkhairedlord Posts: 7,180
    So, replaced the cassette but kept the old chain. :*:#:s
Sign In or Register to comment.