Changing Ultegra cassette

stevez Posts: 29
edited December 2012 in Workshop
I'm thinking of swapping my 11-28 cassette for the 12-30 just to make those hills a little easier!!

I've never done this before but no I need a chain whip and release nut, but once I've fitted the new cassette will I need to adjust the gears at all?


  • StefanP
    StefanP Posts: 429
    You need to make sure the derailleur will accept a larger cassette at the back (Shimano Tech Docs), I'm guessing you'll have a long cage mech already, if you have an 11-28 on there already. You'll need to adjust the B-limit screw of the derailleur and resize the chain. You might have to reindex it a little.
  • smidsy
    smidsy Posts: 5,273
    B screw does not resize the chain it simple moves the top jockey wheel in relation to the cassette (clearance). The chain will still be the same size.

    You may be OK with the chain - just depends how tight it was before.

    With shimano they tell you to size it on the large front chainring and smallest rear cog.

    In theory the size of the big rear cog is irrelevant as you should not use large front/large rear combo anyway.
    Yellow is the new Black.
  • arlowood
    arlowood Posts: 2,561
    Did this swap back in May when I struggled on a 100K sportive with some short steep hills using my lowest 34-28 ratio.

    My experience of the changeover is reported here:- viewtopic.php?f=40004&t=12850935&p=17597505#p17597505

    Generally speaking you should have no problem and you should get away without needing a new chain or rear derailleur. Your gear indexing may need to be tweaked a bit although I got away without needing any adjustment.

    Just be aware that the Tiagra 12-30 cassette does not require a spacer while on most hubs the 11-28 cassette will have a 1mm spacer fitted. Just make sure you remove it if one is fitted before you fit the 12-30 cassette.
  • markyone
    markyone Posts: 1,119
    Is 11/28 not enough :shock:
    Colnago c60 Eps super record 11
    Pinarello F8 with sram etap
  • Monty Dog
    Monty Dog Posts: 20,614
    FWIW 28 is about the limit for most Shimano road rear mechs - the top jockey wheel will hit a larger sprocket otherwise, long cage rear mech or not. If you want to run a larger sprocket, you'll probably need the change the rear mech for an MTB one (needs to be 9 speed as Dynasys is incompatible).
    Make mine an Italian, with Campagnolo on the side..