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Long cage rear mech...

derekwattsderekwatts Posts: 107
edited December 2008 in Workshop
Hi

Just a quickie - I have fitted a 12/27 rear cassette to my bike which has a standard Ultegra rear mech and a 53/39 chainset. There is just a tiny bit of jokey wheel rub on the 27 rear cog which I can live with.

What I am thinking of doing, rather than fitting a compact and having to constantly keep changing cranks every time I take my bike away for some mountain riding, is to fit a 'mountain bike' rear cassette e.g. an 11/32 or a 11/34, and a long cage rear Ultegra mech. Just changing cassettes is a lot cheaper and less hassle than changing chainsets and splitting chains all the time, and is also close to the bottom gear I have been using on rented road bikes overseas that were fitted with a triple (a route I don't want to go down...)

My question is this. Will a long cage rear 'road mech' like the Ultegra 6600 still have sufficient clearance to fit something as big as a 34 tooth cassette?

Thanks

Derek

Posts

  • Gary DGary D Posts: 431
    No.
    If you look on the Shimano website, you will see that the maximum quoted capacity for that mech is 27T. It is generally accepted though that you could push that to 28T (as I have done) or possibly even 30T, but not any more.

    Also, the mech you quoted is a 10 speed. Mountain bike cassettes only come in 9 speed - so your shifters won't work very well, if at all, assuming they are also 10 speed.
    Or are they 9 speed?
    If it is 9 speed, you could consider fitting a MTB rear mech instead of the Ultegra.

    If you need a gear that low, you would probably be better biting the bullet and going for a compact. Personally, I would opt for the triple, as it gives you the best of everything, but you have said that you don't want to go down that route. If you are worried about the looks of a triple, it is going to look no worse than a huge rear mech and a dinner plate size cassette! :wink::wink:

    Hope this helps,
    Gary.
    Oh and I feel like I've been raped by an Orangutan :shock: And I've got legs like Girders :lol:
  • John.TJohn.T Posts: 3,698
    Fit an MTB rear mech. Any Shimano medium cage one will be fine. The mech does not know how many gears you have. The shifter decides that.
    You can fit a 50/34 compact with your present mech and cassette. It is just outside Shimano's recommended range but works fine if you run the chain as long as possible. The tongue on the front of the cage should be just clear of the chain when on small/small.
    As for the jockey rub on the current set up. You should adjust the B screw to clear that. The gears should change better as well.
  • robbarkerrobbarker Posts: 1,367
    It sounds like you need a road triple and long cage road mech.

    In the meantime adjust the b screw on the rear mech to get it working smoothly in the 27 cog - see Park Tools webby for an illustrated guide.
  • alfabluealfablue Posts: 8,497
    As well as tightening the B screw I had to shorten my chain to stop jockey rubbing ( :shock: ). Set the chain so that the jockey wheels are in vertical alignment on the large ring, small sprocket.
  • MettanMettan Posts: 2,103
    derekwatts wrote:
    What I am thinking of doing, rather than fitting a compact and having to constantly keep changing cranks every time I take my bike away for some mountain riding, is to fit a 'mountain bike' rear cassette e.g. an 11/32 or a 11/34, and a long cage rear Ultegra mech.

    Due to a long term knee injury I've currently got a similar setup - ie - 50/34 compact with an 11/32 cassette - that's paired with a Shimano MTB rear mech - depending on whether you've got an 8 or 9 speed setup you can go with something like Altus/Acera/Deore/LX rear mech etc,etc - they're all reliable - (I've been using a supposedly censored one for over a year and its been fine.....).
  • Thanks guys.

    I just want the same or similar ratio to the 30/27 I have been using on the rental bike. I really don't want a triple cos for me it's totally unneccessary for the routes I ride in the UK. In fact even a compact isn't really necessary.

    30/27 = 1.11 and 39/34 = 1.14. A compact with my 12/27 cassette gives a bottom ration of 1.26 which is a little bit too much of a jump up from what I have used so far on the triple. Once I can hack 1.25 I'll just buy a compact and revert back to a road rear mech and my 12/27 cassette.

    I'm pretty fit but I can't do a 15 mile climb at 7% yet, so rather than stopping half way up I would rather just pick a gear that I can complete it and work on my climbing skills. I'm off there tomorrow again so maybe I will try and see if I can do the climb in 30/24 but I doubt it... :shock:

    Cheers

    Derek
  • Gary DGary D Posts: 431
    Derek,
    You didn't say whether you have 8, 9 or 10 speed at the moment?

    If it's 8 or 9 then you could go ahead with a set-up similar to Mettan's. If you intend to then revert back to your 12/27 cassette when you get home, you might start having to mess about with chain length. Therefore, it would probably be worth investing in 2 new chains and keep them with a particular cassette. Probably good practice to do that anyway.

    Not sure what you can do if you have 10 speed STI's though. I know John T made the point about the rear mech not knowing how many gears you have, but the point I was making is that MTB cassettes (11/32, 11/34 etc.) are all 8 or 9 speed and I don't think you can get a 10 speed cassette with that wide a spread - unless you can have one specially made or if someone else knows where you can get them?

    Gary.
    Oh and I feel like I've been raped by an Orangutan :shock: And I've got legs like Girders :lol:
  • Derek

    Use a MTB rear mech. During the course of my many fiddlings and tinkerings, I have used a 53/39 double chainset together with an 11/32 MTB cassette. 9 speed Ultegra shifters and MTB 9 speed XT rear mech worked quite nicely.

    Happy New Year

    Stu
    Living in East Kent has it's perks. France is 21 miles away. A very different riding experience!
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