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Cranks coming loose when it rains!

SaintMarkSaintMark Posts: 68
edited July 2012 in The workshop
It seems like every time I ride my commuting bike in the rain, the next day the cranks start working loose.

I've got an FSA Vero chainset on a Shimano square-taper bottom bracket. I've tightened the bolt as hard as humanly possible without snapping my allen key so anyone know what else I can do?

Does this happen to anyone else when it rains, or is it just coincidence?


  • danlikesbikesdanlikesbikes Posts: 3,898
    Yes it did happen to me a few week's ago.

    Mine turned out not to be the bottom bracket or the crank as both myself & my friendly LBS tried both. What happened was the locking ring had a hair line fracture that in the dry did not affect the crank but in the wet it caused the slightest bit of movement at the joint.

    Whilst the crank set was out of warranty as upgraded circa 18 months ago, the LBS spoke to the manufacturers who did confirm that they had a few issued with the locking nut & had since changed the design & they agreed to replace the whole thing for free.
    Pain hurts much less if its topped off with beating your mates to top of a climb.
  • SaintMarkSaintMark Posts: 68
    Ah-ha thanks, I was getting paranoid. I hadn't thought of closely checking the state of the nut itself. I think I have a spare at home so could do a swap.

    This is the second BB on this bike, the original one kept unscrewing itself from the shell and it was back in the shop twice, so the LBS changed it for a Shimano one which has stayed in place but now the left crank keeps coming off.
  • The RookieThe Rookie Posts: 27,811
    You'll never do a square taper up tight enough with an Allen key, you need an Allen socket on a ratchet, 3/8" drive at least.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • bompingtonbompington Posts: 7,674
    They're not carbon fibre are they? ;-)
  • SaintMarkSaintMark Posts: 68
    Well it's still coming loose. Almost every ride now which is very annoying.
    You'll never do a square taper up tight enough with an Allen key, you need an Allen socket on a ratchet, 3/8" drive at least.

    Hmm thanks I have been putting quite a bit of force through the bolt (don't have a torque wrench) but was worried about damaging it if I did it any tighter.

    I am wondering if the taper and the crank are not quite compatible. Anyone heard of this? I thought all square tapers were the same size but Sheldon Brown says there are two different types. I have FSA cranks and Shimano BB.
  • deswellerdesweller Posts: 5,175
    You'll never do a square taper up tight enough with an Allen key, you need an Allen socket on a ratchet, 3/8" drive at least.

    This, all day long.

    I have a set of long T-handled hex wrenches, but I still stick a bit of pipe over the end when I'm doing square taper crank screws. Not sure what torque I'm putting on there, but it must be north of 70Nm.
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    On Strava.{/url}
  • SaintMarkSaintMark Posts: 68
    Cheers. Have taken your advice and got it as tight as I could using an old seatpost as a lever and my feet to turn it so we'll see how it goes.
  • MichaelWMichaelW Posts: 2,164
    Is the square taper assembled wet or dry? Dry assembly almost fuses together with time; a dab of grease allows for easier removal and possibly, a risk of damaging the taper by excessive torque. Both are recommended, depending on your religion.
  • SaintMarkSaintMark Posts: 68
    I always use a thin layer of grease because I find dry means they creak too which drives me mad. Much as I want the crank to stay on I don't want it seized as I wreck bottom bracket bearings on a regular basis, don't know why, it's always been the part of a bike I seem to destroy first.
  • You may wish to check that the LBS have not mixed Campy and Japanese tapers.

    If you did not inspect/install the BB yourself then it may be worth checking that it is indeed Shimano (JSA) and also that the crank is definitely Shimano too.

    Although the specs are theoretically incompatible they look and feel very similar and it is possible to screw together wrong cranks/BBs but the mating is very insecure.


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