Chain slipping, inner front ring only and can only use first 4 gears

DCI Gene Hunt
DCI Gene Hunt Posts: 138
edited July 2019 in Workshop
Chainrings are 10 speed Shimano 105 double and rear cassette is Shimano 105 11-28. The chain is fairly new but the cassette has miles on it. If I'm in outer chainring I can select all 10 gears if I wanted to. If I'm in inner ring I can only select 4 biggest cogs closest to the spokes without slipping occurring. Chain isn't trying to jump to another cog, it's just like it's riding over the rear cogs from gears 5 to 10 if chain is on front inner ring.

Any thoughts on cause and what to do to resolve situation ?

Thanks

Comments

  • faster97
    faster97 Posts: 33
    The cause is a almost certainly a worn cassette. They can look pretty much perfect, but still slip.

    How fairly new is the chain?
  • DCI Gene Hunt
    DCI Gene Hunt Posts: 138
    I have a new Shimano hg500 12-28 cassette, if I wish to install it for 10 speed use with 105 5701 shifters and a rear wheel fitted with tiagra hub, do I need a 1mm spacer to fit behind the cassette ?
  • keef66
    keef66 Posts: 13,123
    Classic signs of a new chain / worn cassette.

    Only 10 speed cassette which doesn't need the spacer on a 10 speed freehub is Tiagra /HG500 which has it built in. So I'm guessing no.

    I've known this for ages, but when I recently replaced a 10 sp 105 cassette with a Tiagra one I forgot all about it and left the spacer on the freehub. Miraculously I managed to tighten the lockring, but when I put the wheel in the bike the smallest sprocket was fouling the frame. And then the penny dropped...

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