Anyone use SS mtb for SS CX? Need gearing help- Mtbr.com
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  1. #1
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    Anyone use SS mtb for SS CX? Need gearing help

    So I'm planning to build up a SS 29er soon and was thinking about also being able to use it for SSCX (I already have a gear CX bike).

    I'm not sure what gearing to run but was wondering if I could get away with just one chainring that would be able to work for both MTB and SS.

    A couple ideas...

    1) Get a 32T or 34T chainring and just put a small 13/14/ tooth cog for CX. Is there a downside to having too small of a rear cog? Also, it seems like most people use a 32T chainring, why is that?

    or

    2) Just get a 40T chainring and chain for CX (obviously downside is buying another chainring and cog and chain)

  2. #2
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    Sounds like a good time for a dingle...run 36/32 in the front and 14/18 out back. Really depends on what gearing you want, which will be dictated by what kinds of courses you're running.

  3. #3
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    I'm interested in hearing what others recommend. I've never tried CX and might give it a go with a SS MTB this year.

    For your first question, I think the main downside of running a small cog is that it can wear relatively faster and then create more wear on your chainring and chain. I suppose it depends what kind of cog you're running--I know aluminum ones wear out quickly but the cheap stamped steel ones seem to go forever. That is, if you can run one without damaging your freehub.

  4. #4
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    Yep. That bike is a 33x20

    Attachment 1066129

  5. #5
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    Quote Originally Posted by jmctav23 View Post
    Sounds like a good time for a dingle...run 36/32 in the front and 14/18 out back. Really depends on what gearing you want, which will be dictated by what kinds of courses you're running.
    That sounds interesting. How exactly does that work or get set up?

    I'm also in Seattle but tend to go down to the Cross Crusade CX races in Portland.
    The courses here are truly variable. Some are pancake flat and others have more hills...

  6. #6
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    Quote Originally Posted by arphaxhad View Post
    Yep. That bike is a 33x20

    Attachment 1066129
    that's funny! i hope that course had a lot of climbing, though it doesn't look like it from the pic. I'm guessing you spun like a rabid hamster and still didn't make the podium?

    OP, i would either dingle, or just buy two separate chainrings with the same rear cog. use a separate chain for each chainring. something like 32:18 and 39-42:18. it still keeps it pretty simple and you can swap it out in a couple minutes.

    the biggest compromise IMO would be tires. which i would swap out too.
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  7. #7
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    Quote Originally Posted by *OneSpeed* View Post
    that's funny! i hope that course had a lot of climbing, though it doesn't look like it from the pic. I'm guessing you spun like a rabid hamster and still didn't make the podium?

    OP, i would either dingle, or just buy two separate chainrings with the same rear cog. use a separate chain for each chainring. something like 32:18 and 39-42:18. it still keeps it pretty simple and you can swap it out in a couple minutes.

    the biggest compromise IMO would be tires. which i would swap out too.
    Yeah, I'm starting to thing just get 2 chainrings/chains would be the way to go... unless someone can explain what the heck a dingle is and how it works?!

    No worries on the tires. I have a box full of CX tires from file to mud tread (from prior use my geared bike).

  8. #8
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    Quote Originally Posted by truongasaurus View Post
    Yeah, I'm starting to thing just get 2 chainrings/chains would be the way to go... unless someone can explain what the heck a dingle is and how it works?!

    No worries on the tires. I have a box full of CX tires from file to mud tread (from prior use my geared bike).
    You run a double crankset with something like this in the rear: Drivetrain | Parts and Accessories | Surly Bikes

    Or I suppose you could put two cogs on a cassette hub, using spacers to line up the chainline.
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  9. #9
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    I run 36x22 for mtb and 36x18 for CX. Both work really well and it means I do not have to swap out chainrings. I can get away with the same chain if I set it up perfectly.

  10. #10
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    I would make it easy on yourself and just have a dedicated chain ring, cog, and chain to swap out for each. Only takes a few minutes for less compromise and/or complication of running the same gear for both or a dingle setup of some sort.
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  11. #11
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    Dingle speed is as simple as single speed two times. Assuming you have a standard free hub with spacers on the back, you just put two cogs on instead of one. Assuming you have a crank that can accommodate two chainrings (inner and outer positions), you mount the 32 on the inside with the 18 tooth cog lined up on the inside out back. Mount the 36 tooth chainring on the outer position on the crank in line with the 14 tooth cog out back. Overall tooth count is the same so the same chain can be used with maybe some minor adjustment to optimize chain tension.

    It gets more complicated if you're running a freewheel out back then your only option is a white industries dos eno freewheel.

  12. #12
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    I ran 34/17 on the CX bike and 34/20 on the MTB for CX.
    If it's flat, it's either rough or boggy on the tracks the masochists here design.

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