Will my Tiagra GS take a bigger cog than 27 teeth?

henryrym
henryrym Posts: 14
edited October 2007 in Workshop
Hi

I run an old steel road bike for commuting. At the moment I run an 8-speed 12-23 cassette with a Tiagra GS rear and a triple front. I'm wanting to spend half term in the Dales doing a bit of cycling. It's a lot more hilly than I'm used to and I'm nearly 60 and fat, hence I want more teeth on my cassette!

The spec for long cage Tigra rear specifies 27 teeth as max. What happens if I have more than that - 11-30 MTB cassettes are cheap and plentiful. I don't mind a poor change into bottom occassionally. I will only use bottom gear with my granny ring. What about going for an 11-32? Would that work?

Thanks
Henry

Comments

  • maddog 2
    maddog 2 Posts: 8,114
    no.

    road mechs (short OR long cage) will only go to 27t (officially) and 28t-ish (practically). Some people have stretched this to 30t but you can't guarentee this will work for you.

    to go more than 28t then you'll need an mtb mech. The geometry of mtb mechs is different, that's why.

    You could try one of these - XT 11-28

    http://www.chainreactioncycles.com/Mode ... ModelID=47

    11-28 with a triple up front will give you a pretty low gear. LX is also available for £20.

    If you don't fancy that then you could get a 13-26, which would definitely work with a road mech.

    http://www.chainreactioncycles.com/Mode ... delID=1864
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • henryrym
    henryrym Posts: 14
    Many thanks Maddog 2 for such a definitive reply!

    I'll go for an 11-28 and see how I get on.

    Thanks
    Henry
  • shockedsoshocked
    shockedsoshocked Posts: 4,021
    I bought a 27-12 cassette by accident using the same deraillier as you, and it caused the jockey wheels to rub the actual cassette. It still worked, but you had an annoying bumping noise everytime you used that gear.
    "A cyclist has nothing to lose but his chain"

    PTP Runner Up 2015
  • maddog 2
    maddog 2 Posts: 8,114
    try tweaking the tension screw on the mech ShockedSoShocked

    that should rotate the mech a little and may stop the chain rubbing.

    the truth is that some setups are prone to rubbing and others get away with 28t or even 29t. Chain tension is part of it but I suspect that frame dropouts differ in their position. Some frames have a lower dropout so they can accommodate bigger sprockets.

    Suck it and see. New cassettes sell well on ebay so you'll only lose a few quid experimenting.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer

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