cassette swap - index issue

chiv30
chiv30 Posts: 49
edited April 2012 in Workshop
Hi all new to road but previous mtb rider so not totally green .
Apologies if this has already been covered elsewhere, but iv not been able to find the answer..
I have just replaced the 11-25 rear shimano 105 cassette for a 12-28 Tiagra cassette and expected a straight swap with no issues, ill admit iv not replaced the chain but its done less than 100 mile.

Anyway the problem is there was what seemed to be a shim behind the 105 cassette which iv had to remove to enable the lock ring to tighten on the Tiagra , I assumed the cassette swap wouldn't need any fine tuning of the indexing however I seem to be slipping in 3rd and 4th so I'm wondering is it down to the shim removal or just a case of slightly different cog thicknesses on the two cassettes?

Anyone else made this swap and had the same issues and if so did tweaking the indexing resolve it?

Bike is a Scott S20 full 105 bar the new cassette and an ultegra rear mech.
Thanks

Comments

  • bus_ter
    bus_ter Posts: 337
    All 10 speed shimano cassettes come with a shim or 'spacer' which you need to fit. You only don't fit this with a 10 speed only hub. Some wheels come with a shim/spacer too that you need to fit with the cassette.

    Anyway ignoring that, it could be the new cassette jumps is because of wear. A slipping chain isn't an indexing problem. Possibly your chain and cassette have worn together out of shape, and now the chain doesn't match the new cassette? Maybe you need a new chain? Going from a 25 to a 28 should mean a slightly longer chain anyway.

    EDIT: Just read your chain is also nearly new.. So I don't know?? :?
  • chiv30
    chiv30 Posts: 49
    Appreciate that response , as I've come From mtb ive only ever dealt with 9 spd setups , I wasn't aware that all shimano10 spds used a shim.

    No matter how I tried , I couldn't get the lockring to catch with the original shim at the rear of the cassette so I removed it and all seemed fine , ie , no lateral movement whilst rotating,
    I'm now wondering, even though the Tiagra didn't come with a shim, that the removal of the shim could be causing the slight issue :/
  • desweller
    desweller Posts: 5,175
    You've definitely bought a Tiagra 10-speed block and not the previous model 9-speed?
    - - - - - - - - - -
    On Strava.{/url}
  • John.T
    John.T Posts: 3,698
    Tiagra 10sp does not use a shim. (Just to confuse us.) It should go straight on and it should also not need any index adjustment.
    See post above.
    My Fleet.
  • hodge68
    hodge68 Posts: 162
    I know this is not very helpfull, but im just letting you know it does work.I have 105 and got the LBS to swop over the 11-25 to tiagra 12-28 +new chain and apart from a little cable adjustment after a week or 2 it works great.I think the older 105(like mine) is only rated to max 12-27 along side a compact,as i said to may shame :oops: the LBS does all my work so not sure if they adjusted the B screw on the back of the mech.Sure there is plent on here about it, as i looked into to prior to getting the work done.Good luck
    Ridley Boreas
    Spesh RockHopper pro
    Boardman cx comp

Categories