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  1. #1
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    determining crank arm length and more

    This all started when I decided to overhaul my bottom bracket while I was in the process of converting my road bike into a fixed gear. Cavet - I do a lot of my own mechanical work on cars, just starting to get into the bike mechanics stuff.

    I bought this bike used, it is a Miele road bike with a square taper bottom bracket with bearings, NOT a cartridge BB.

    I popped the dust covers off the crankarms and saw that the threads that the crank arm removal tool threads into are totally roached, gone, trashed. There is no way to thread the tool into the crankarms and get it to stay. I tried, and I just ended up pulling the tool out when I cranked the inner bolt onto the axle attempting to take the crank arm off (what the hell, the threads were already pretty far gone).

    I then looked more closely at the crank arms and saw that one is 170mm and the other is 172.5. Joy. Oh well.

    My current thinking it to pry the crank arms off with a gear puller or ball joint puller, and if that fails, cut the sum*****es off with a wizzer tool (gotta love compressed air tools ). Current thinking goes, if I have to cut the crank arms off I will go ahead and replace the old BB with a cartridge style BB and get new crank arms (which will only run a single chainring up front)

    Problem is I have no idea how to determine the proper crank arm length. I am a 5'5" shorty with a pant leg inseam of 31 or 30" depending on the manufacturer of the pant. Soooo, do I get 170mm cranks, 172.5mm, 175, etc. and how do you figure that out? I figure I won't know what cranks to get until I figure out what BB cartride I need to replace the old BB.

    Sorry for the length, but I have been enjoying a couple of fine and I tend to ramble.

    Thanks!

    Victor

  2. #2
    Scooby Snax
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    Give
    airborne a try, they have some fitting cues online.


    Scoob

  3. #3
    opinionated SOB cycletourist's Avatar
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    Sounds like you might be happy with 165mm crankarms.

  4. #4
    Oh God, He's back! 1oldRoadie's Avatar
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    crank arm length is more in ratio to your thigh length than anything else. If you are long legged for your height you might need a long crank arm r=than you suspect.
    I can't ride and Frown!

  5. #5
    Kev
    Kev is offline
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    I think crank arm length is more of a personal choice, there has been posts about this in past, people with longer legs using 165, and people with shorter legs usign 175. I know I have 175 length cranks on all my bikes and I'm 5'7" and my inseam is 31".

  6. #6
    Senior Member late's Avatar
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    Hi,
    my legs are a little shorter than yours, and I ride a 170mm. A 28" inseam is sometimes a little long. It's a matter of personal preference. The threads in the frame are delicate; it might be a good idea to let a bike shop yank that out.
    Measure the difference in length between your left and right legs. That you didn't notice the difference in crank arm length makes me curious. Some guys with a leg that is longer prefer different length crank arms. I think it's a cool idea; but have been too lazy to pursue it.
    We are as gods, we might as well get good at it.
    Stewart Brand

  7. #7
    Senior Member mechBgon's Avatar
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    All you need is to get the left crankarm off, or chop the spindle on that side, and then you can remove the right crank + spindle + driveside bearing cup in one chunk and toss it.

    One way of removing the left arm is with a pickle fork, if you've got one, or you can simply chop it like you said.

  8. #8
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    I ended up chopping the left side crankarm off with the wizzer. I pulled out the bearing race and cup and saw that there was almost no grease left! Ouch. I think I am going to replace the BB with a cartridge style which means that I am in the market for a new set of cranks too given that one of them is unusable.

    Thanks for the bike fitment links, I'll check those out.

    Victor

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