New frame needs some drive train advice- Mtbr.com
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  1. #1
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    New frame needs some drive train advice

    I put this in the Trek and the drive forums and no replies. I was hoping I could get some help from the WW group.

    I am not a WW but I plan on getting a Trek Elite 9.9 frame in the next two mths.

    At this time I will also upgrade my drive train.

    I will go 2 x 10 and I like Shimano shifting over Sram. However I like the 42x28 gearing much more than the 30x42 or the 28x40 gearing.

    How can I get a 42x28 gearing with shimano shifting? I was thinking about getting a rotor 3d crank but I donít like their Q rings. Would the extralite 42x28 rings work with rotor?

    Also could I get a RF next sl at 30x42 and then change out the 30 ring for a 28 ring?

    FSA makes a 42x27 crank. Their weights sort of suck compared to other cranks and I donít know if it would work with a BB90.

    Lastly this will be a BB90 set up so I would need the crank to work with that. How much of a tradeoff would I be making by getting a non shimano 42x28 set up? Meaning I love that gear ratio but I donít want to sacrifice too much front end shifting by mixing brands together.

    Thanks in advance for your help.

  2. #2
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    You could always buy a new 28T XTR chainring to build the 42-28, the rings will fit on the 985 42-30 cranks and the front derailleurs will cover a 40-44T big ring. The shift ramp clocking might not be exact.
    I'm a member of NSMBA and IMBA Canada

  3. #3
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    I see three options.

    1 - as above, buy a 30/42 M985 crankset and swapping the 30 tooth for a 28 tooth. Shift gates on the 42t big ring are placed to work with a 30 tooth so it won't be AS good. Being Shimano it'll still be fantastic.

    2 - just use a SRAM XX crankset with 28/42. One of the big positives to the XX group is the chainring stiffness and shift quality. Shimano chains work well with them so no issue there.

    3 - buy a 104/64bcd or 110/74bcd crankset such as Rotor 3D or Agilis and use Specialties TA chainrings instead of Rotor Q-rings. These are light and shift very well. The best of aftermarket chainrings.

  4. #4
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    "Shift gates on the 42t big ring are placed to work with a 30 tooth so it won't be AS good"

    Dam I never even thought about that. Has anyone done this before and whats your experience? I really like the XTR 985 crank. Their version even though being aluminium is still very competitive in weight to carbon counter parts.

    I feel weird asking all these what if questions. But I need to, I don't have enough money to blow on different parts to get a feeling of how it feels and then choosing the one I like best.

    Two options. XTR 42x30 and getting a 28 spare chaining and switching. My front end shifting won't be as good.

    2nd option: running an XX crank with everything else XTR.

    Between the two what kinds of differences would I notice with front end shifting?



    I think that will end up making my mind up.

    Thanks again for the input.

    WW section rocks

  5. #5
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    Q factor on the XTR cranks should be a few millimetres narrower.
    I'm a member of NSMBA and IMBA Canada

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