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  1. #1
    driving sucks indianatrails's Avatar
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    Bottom bracket keeps coming loose

    ...and it has only ~1000 miles on it. I've tightened it a few times (both sides). Should I just replace it? It's a Shimano, square taper 68x11?, on a Bianchi Bergamo (hybrid). The drive (right) side seems to be coming loose most often, which threads in reverse (lefty tighty). Could there just be too much friction within it, putting torque on the drive side threads as I pedal? Thanks in advance!

  2. #2
    Senior Member Retro Grouch's Avatar
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    What have you been tightening it with?

    The torque spec for Shimano cartridge bottom brackets is around 30 lb/ft. Imagine a 30 lb weight hanging off of the end of a foot long wrench handle. That's more than I'd probably use if simply left to my own devices. If it was my bike I think that I'd remove the bottom bracket completely, grease the threads and reinstall it tightly.

    If anything, pedaling procession should actually tighten the bottom bracket within it's shell.

  3. #3
    Senior Member MudPie's Avatar
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    Quote Originally Posted by Retro Grouch View Post
    What have you been tightening it with?

    The torque spec for Shimano cartridge bottom brackets is around 30 lb/ft. Imagine a 30 lb weight hanging off of the end of a foot long wrench handle. That's more than I'd probably use if simply left to my own devices. If it was my bike I think that I'd remove the bottom bracket completely, grease the threads and reinstall it tightly.

    .
    +1 proper torque is your friend. To get that 30lb-ft of torque, I'm typically using an automotive type of torque wrench, 1/2" socket, 15" handle length. It's more than most people imagine.

  4. #4
    driving sucks indianatrails's Avatar
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    I borrowed a Park BB tool and gave it a crank (that was some terrific imagery for torque, by the way, thanks!) Been meaning to get a torque wrench, so if it loosens again, there's my excuse. I'll take your advice and set to 30lb/ft. If precession wasn't the cause of the loosening, I'm still trying to understand what's up with it.

  5. #5
    cab horn
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    Properly greased and torqued bb's should not come loose.
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

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