• 05-09-2014
    cobi
    Day #2: almost had to call the wife for a ride!
    That's gotta be a record for a mechanical that almost warrants calling the wife! Here I was worried about running tubes and my CRANK ARM FELL OFF! Not the most optimistic start to my commuting venture!

    Due to not having a good secure place and not having a bike setup well for commuting I figured I'd start off on my wife's old mtn bike (old rigid 3x7 diamond back) to see if I stick with it.

    Had heard some creaks and such but didn't think much of it, then the pedal started wobbling and I saw the problem, eventually the crank came off! Since I didn't have a socket wrench on me I was pretty much screwed, it's a 12mm or so head bolt that threads into a square BB. Was able to sorta pound the arm on with my hand and hand-thread the bolt but it would only last 1/3 of a mile or so. Limped home stopping to tighten multiple times.

    Need to setup a better bike I think but that's for another post.
  • 05-09-2014
    mtbxplorer
    Not to worry, it's happened before, and usually the "victims" installed the cranks themselves. Consider asking a good shop to check as much as they can for whatever $ amount you can spare, $20 or higher. They will likely also advise what else is coming down the road to fix/replace.
  • 05-09-2014
    cobi
    Bike really isn't worth spending the money on to tune up frankly. It shifts great, stops ok. As long as the crank doesn't fall off again it will do for now.

    But it's sat outside under a tarp the last few years. I posted another thread looking at options for my continued commuting adventures, this bike is just to hold me over till I decide what to replace it with.

    I just was laughing at the thought of calling my wife to rescue me on day 2. I'd never hear the end of it!
  • 05-11-2014
    car bone
    Now that it has fallen off once it has probably ruined the interface and will continue to fall off. The trick with cranks and pedals is to torque down as hard as you can with plenty but not ridiculous leverage, and they will never ever fall off again.
  • 05-15-2014
    cobi
    Quote:

    Originally Posted by car bone View Post
    Now that it has fallen off once it has probably ruined the interface and will continue to fall off. The trick with cranks and pedals is to torque down as hard as you can with plenty but not ridiculous leverage, and they will never ever fall off again.

    You called it! Came off again on the ride home. I thought I had torqued it down pretty good last time. Will lock tight help? Supposed to pick up my new commuter tomorrow anyway, but don't wanna sell this if the cranks are gonna fall off on the next poor bastard.
  • 05-15-2014
    BrianMc
    Crank loose/falls off | Bike Boo Boos

    "Square taper bottom brackets have just that a square, tapered end to the bottom bracket axle. These sometimes wear too small, so try to shim the crank-to-bottom-bracket interface with strips of aluminum can or similar."

    Good luck. The crank arm hole can wear too large too.
  • 05-16-2014
    CommuterBoy
    When I had square taper failure back in the day, it was the aluminum crank arm that wallowed out, and not the BB that took the damage. I wound up having to get a new crank arm. The aluminum can shim thing sounds like a good idea though....
  • 05-16-2014
    jrm
    Better that then having to beg your way onto the bus b/c you dont have exact change. Maybe you can find a bolt at the hardware store so that you can @ least attach the crank arm. Use loctite on the threads..