Non-drive crank working loose

bompington
bompington Posts: 7,674
edited July 2019 in Workshop
... about 12 times on a 2½ hour ride today.
First noticed it loose yesterday: stopped to tighten up and it seemed fine. For about an hour.

By the time I got home today it was palpably loose about every 15 minutes.

No sign of stripped threads or cross-threading; it feels like it is tightening proper and solid.

Any suggestions before I go and shell out on new bits?

Comments

  • wongataa
    wongataa Posts: 1,001
    What brand cranks do you have? Different cranks have different connection methods so any possible fixes will depend on what you have. If something threaded is coming out have you tried threadlock?
  • Alejandrosdog
    Alejandrosdog Posts: 1,975
    bompington wrote:
    ... about 12 times on a 2½ hour ride today.
    First noticed it loose yesterday: stopped to tighten up and it seemed fine. For about an hour.

    By the time I got home today it was palpably loose about every 15 minutes.

    No sign of stripped threads or cross-threading; it feels like it is tightening proper and solid.

    Any suggestions before I go and shell out on new bits?

    Any sign of a hairline crack on the crank?
  • StillGoing
    StillGoing Posts: 5,211
    bompington wrote:
    ... about 12 times on a 2½ hour ride today.
    First noticed it loose yesterday: stopped to tighten up and it seemed fine. For about an hour.

    By the time I got home today it was palpably loose about every 15 minutes.

    No sign of stripped threads or cross-threading; it feels like it is tightening proper and solid.

    Any suggestions before I go and shell out on new bits?

    FSA had a real problem with NDS crank arms coming loose. Only thing you could do was use copious amounts of thread lock and check regularly.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • frisbee
    frisbee Posts: 691
    philthy3 wrote:
    bompington wrote:
    ... about 12 times on a 2½ hour ride today.
    First noticed it loose yesterday: stopped to tighten up and it seemed fine. For about an hour.

    By the time I got home today it was palpably loose about every 15 minutes.

    No sign of stripped threads or cross-threading; it feels like it is tightening proper and solid.

    Any suggestions before I go and shell out on new bits?

    FSA had a real problem with NDS crank arms coming loose. Only thing you could do was use copious amounts of thread lock and check regularly.

    I had to cut my FSA crankset off with an angle grinder!
  • StillGoing
    StillGoing Posts: 5,211
    Lots of results for FSA cranks coming loose from 2006 to 2018 on a quick Google search.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • bompington
    bompington Posts: 7,674
    ...it probably would have helped if I'd mentioned the make and model :oops:
    SRAM Force GXP it is.

    So I gave it a really good clean and then reassembled it complete with loctite and pretty high torque.
    It seems to have worked - survived a 25 mile pootle yesterday that did include some fairly vicious hills.

    Still can't work out why though.
  • keef66
    keef66 Posts: 13,123
    Seems it's a common issue. Which suggests it's either poor design / specification, manufacturing, or quality control, or possibly all three.

    The bolt securing the blade on my cheapo Screwfix multitool started coming loose after a few days use. Adding thread lock and a toothed locking washer seems to have sorted it

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