Mixing an XT 11-42 cassette with a 105/Tiagra drivetrain

big lewy
big lewy Posts: 35
edited September 2015 in Workshop
Hello,

I have been looking for a gravel/cross type bike with discs and eyelets for a rack, plus gearing suitable for touring (ie a low bottom gear sub-25"). Very difficult it seems.

Then I came across an XT cassette with a 42 cog an thought it could be the answer to my problems when paired up with the typical cross or road chain sets/drive trains on the bikes that I have been looking at.

Can anyone advise me about any technical difficulties in trying to mix and match components like this? Would I have to change the rear mech as well to accommodate the range of gears on the cassette or would a 105 long cage do the job?

All useful advice appreciated, thanks.

Comments

  • arlowood
    arlowood Posts: 2,561
    The XT cassette you have identified is an 11-speed variant so your other components will have to be 11-speed to be compatible. Also the XT range of cassettes is aimed specifically at MTB usage, as far as I gather, so there may be compartibility issues with pull ratios and indexing if you are using road shifters.

    If you are running 10-speed (as I surmise since you mention Tiagra in the title and that has not yet migrated to 11-speed) then you should be looking at the HG (hypergide) range of cassettes which are compatible with road shifters such as 105 5700 etc. One of the widest ratios available is 11-36 in 10-speed

    http://www.evanscycles.com/products/shimano/hg81-slx-10-speed-cassette-ec023702?country=GB&currency=GBP&esvt=1008-GOUKE300062&esvq=&esvadt=999999-0-33526-1&esvcrea=61235147456&esvplace=&esvd=c&esvaid=50080&gclid=CjwKEAjw-IOwBRD1wrTC27fSjFISJABUDZ17M5BifwtL1hiAOM18hMJ68C-6iDu1CuWU1VSQYtZbxBoCohPw_wcB

    Not the whopping 42 tooth lowest gear but better than some of the standard cassettes that only go to 30 tooth.

    This HG cassette will definitely work fine with a 105 long cage rear derailleur and should also be OK with a medium cage such as the 105 RD5700 GS

    http://www.wiggle.co.uk/shimano-105-rd-5700-rear-derailleur/
  • would mtb chainset e.g. 42-32-22 with a 11-30 road cassette give you a good enough range?

    19.8 inch easiest gear
    104 inch hardest gear
  • A triple would be ideal and what I have on my Galaxy, where I have a Deore chain set and rear mech, with a Tiagra front mech. However, not yet found a bike with this and other req'd spec off the peg, and I do not want to buy another out-and-out tourer.

    Any ideas?

    A 34-36T road set up would probably be next best solution, and would give me a wider choice of bikes. However, I can still remember grinding up Bealach Na Ba this July in the 21.5" gear on my Galaxy............ (plus the terrifying descent in the rain with the weakly effective cantilever brakes - hence the need for discs).
  • can get MTB double chainsets as well as triple - don't think you'll find the ratios you seek off the peg

    with a long cage road mech you can go 11-32 and 34-50 compact road chainset which is a 28 inch gear

    otherwise i think you'll need a different chainset/mech

    your LBS might be happy to swap out things like that on a new bike - can always ask
  • arlowood
    arlowood Posts: 2,561

    with a long cage road mech you can go 11-32 and 34-50 compact road chainset which is a 28 inch gear


    He could push that a bit further (~25 inch gear) if he opted for the 11-36 HG81 SLX cassette I've linked to above with a 50/34 compact chainset and long cage rear mech. Still a bit removed from the 21.5 inches he could achieve on his Galaxy.
  • Monty Dog
    Monty Dog Posts: 20,614
    10-speed Shimano road shifters and 9-speed MTB mech will work with a 10-speed 11-40 cassette/expander with no modification. 42 expander can be used with a longer b-screw. If you're riding laden offroad you'll probably want to go with a triple chainset i.e. 30 inner chainring.
    Make mine an Italian, with Campagnolo on the side..
  • davidof
    davidof Posts: 3,062
    can get MTB double chainsets as well as triple - don't think you'll find the ratios you seek off the peg

    with a long cage road mech you can go 11-32 and 34-50 compact road chainset which is a 28 inch gear

    Nice, that is what I was riding this morning on a km stretch at 16% with ramps of 21%. I use a short cage Ultegra derailleur. That's using an SRAM cassette.
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