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  1. #1
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    BMX Crank on a MTB?

    hey i picked up a CCM 29er really cheap new, and well that explains it haha.anyways one really weak point on it i found are the cranks i'm a big guy and when i stand up and power down on the pedals like i would on a bmx the cranks and sprockets twist and cause the chain to rub on the derailleur i have adjusted them to death and just want to take them off completely.

    i also have a haro mirra bmx bike with a 3 piece crank but it is left side drive can i make this work on my mtb ?
    i assume i'll need chain guides too possibly? the bike is a 21 speed

  2. #2
    workin' it Administrator
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    unless the BMX bike has a Euro bottom bracket you will need to source a Euro BB for your BMX cranks as well.

    A euro bottom bracket is smaller in diameter than a BMX standard BB. Possibly a good solution for you would be to go to a 1x9 setup, eliminating the front derailleur and large and small chainring and replacing them with a bash guard (http://www.jensonusa.com/store/sub/1...ashguards.aspx) and a n-gear jumpstop(http://www.gvtc.com/~ngear/whatis.html).

    This will eliminate the front derailleur rubbing.

    Alternately there are numerous cranks out there that are probably stiffer and better than the ones on your CCM but that is a much more expensive option.
    Try this: HTFU

  3. #3
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    ok i see what your saying, so this would also eliminate the need for a chain guide, and i only have 7 gears in the back so it would be a 1x7? and then i can just remove the chain rings, how hard is it to do that?

  4. #4
    workin' it Administrator
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    CCM 29er This bike right?

    Looks like you can easily remove the chainrings, the chainguard will replace the large chainring and the smaller ring will probably remove as well. Depending. It might not in which case you would just leave it on.

    I can see why the bike might flex, the chainrings look like stamped steel which isn't the stiffest material. You might look at also getting a new front chainring: http://www.blackspire.com/qs/product/83/5948/263230/0/0 (canadian company). They also sell chainguards.

    Finally you might check either online bike shops for a singlespeed specific crank: http://www.jensonusa.com/store/produ...ankset+11.aspx or http://www.pricepoint.com/detail/143...kset--2010.htm

    then you just need the jump stop and you are good to go with substantially stiffer cranks and chainrings.

    or surf the MTBR Classifieds for a new crank, used crank or stuff you need: http://classifieds.mtbr.com/index.php
    Try this: HTFU

  5. #5
    Cars Are Evil
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    Replace the cranks. Those are likely square taper and will fail soon.

  6. #6
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    would it be possible to just for now because i want to get out biking for cheap as possible atm to remove the derailler keep all the chain rings on and use the large on as a bush guard and get a n-gear for the inside?

    also when i decide to get a new crank set how do i order one? and make sure i get the right one for my bike, i will likely go with a single speed set up what else do i need?

  7. #7
    workin' it Administrator
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    have a look at http://www.bbgbashguard.com/Mountainbike.html for a bashguard. More than likely your bike has a 104 bolt circle. Cheap and will ship world wide.

    I would ride it as is for the time being. You can either "adjust" your front derailleur to not rub with a pair of pliers, also make sure that it is parallel with the chainring (that is not rotated on the seat tube).

    order the right parts and go from there.

    All cranks I listed above should work no problem but if you are installing them yourself factor in the price of the tools to install which would include the tools to remove the original cranks and bottom bracket and the tools to install the new bottom bracket and a set of hex wrenches to install the new cranks.

    Most people use 175mm cranks and the Bottom brackets are Euro threaded and come in either a 68 or a 73mm width which all bottom brackets will fit with spacers. You will need to be able to shorten your chain once converted to 1x9 as well to prevent the chain from flopping too much so you will need a chain tool and some know how.

    Check out the park tools website for helpful tutorials on all the above and check out the Beginners forum here at MTBR for other tips and tricks.
    Try this: HTFU

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