Non-driveside crank falling off (not running enough thread to lock)-Question

Home Forum Bike Forum Non-driveside crank falling off (not running enough thread to lock)-Question

Viewing 23 posts - 1 through 23 (of 23 total)
  • Non-driveside crank falling off (not running enough thread to lock)-Question
  • hora
    Member

    Abit of a waffle:

    Ok, my Saint cranks are only two years old. Cosmetically they are battered but structurally great. I’ve been running a Superstar chain guide in addition to two spacers on the driveside which has left (admittably **** stupid..) a gap that only allowed a small part of the crank end cap thread to enable grip/preload.

    Ergo- the end cap worked itself loose and fell off during my ride- crank arm wiggled abit BUT I was able to descend and pedal without the pedal rotating against the pedals thread.

    My thinking is – if there is enough spline(?) left on the inside of the non-driveside pedal and on the axle then I should be ok to refit a new end cap AND fit the cranks on properly this time?

    Has anyone experienced a non-driveside cranks working itself loose like this? What was the outcome? Could you save/reuse the cranks?

    My thinking is If I lock it up tight/properly (bought a narrow wide ring) I should ‘save’ my cranks for longer?

    Premier Icon wwaswas
    Subscriber

    My experience with anything splined is that once they’re worn/damaged they come loose whatever you do.

    Having said that the end cap is only there to preload the bearings it’s the bolts in the crank arm that hold it on (think headset top cap and stem – it’s the stem bolts that stop the headset coming loose once you’ve finished fitting it) – so I’m surprised the crank arm came off if the bolts were still tight.

    LoCo
    Member

    knackered replace it

    hora
    Member

    wwaswas I even took the black plastic sleeve out from inbetween the bolts pinch-slot to see if I could crank in anymore to hold the cranks on. They still slid off even with alot of effort on the bolts.

    Loco I’d love a new crankset- everythings overpriced at the mo πŸ™

    Scamper
    Member

    My SLX crank arm slowly works itself loose (so far only by only 1cm), regardless as to how tight I do the crank bolts up.

    Premier Icon buck53
    Subscriber

    I’ve had this recently on Deore cranks on the commuter I built up.

    It’s fine now, I removed a spacer from the drive side to show a bit more crank, cleaned everything to make sure it was all pushing up correctly and paid a lot of attention to correct tightness of preload cap and crank arm bolts.

    As long as you didn’t put too much force through the cranks and do a proper job it should be fine, I’d have thought.

    EDIT: Pics didn’t come up for me the first time I posted. Those look a bit far gone imo, don’t think you’ll stop them working loose, but you might be able to mitigate it to a certain extent with proper setup.

    Premier Icon wwaswas
    Subscriber

    They still slid off even with alot of effort on the bolts.

    I think you’ve answered your own question.

    Use a torque wrench and thread lock on the clamp bolts. I’ve taken the preload cap off some cranks after fitting and never had problems.

    Premier Icon sillyoldman
    Subscriber

    1st thing to do is correct the spacer set up on your BB. If a 68mm shell, then 1 spacer on either side plus your chain guide on drive side, or if 73mm then only the chain guide used as spacer.
    That’ll cure your spline overlap issue, and correct your chain line too.

    The reduced spline overlap may have contributed to the crank working loose, but generally this is caused by the pinch bolts not being evenly torqued.

    Get a new preload cap, and a torque wrench, sooty out your shonky BB spacing, and it should be fine.

    Edit – just read how fooked your splines are. Add a non-drive arm to the above shopping list and follow the same instructions….

    Premier Icon binners
    Subscriber

    Its a warranty claim surely? Send them to Japan, recorded delivery

    tops 5
    Member

    I had 2 SLX cranks fail like this – it was terminal. Had something similar with XTs (dont think I tightened them up enough) and they have been fine.

    I was wondering whether to replace the plastic pre-load spacer with an alloy one and loctite it in place. I know its not designed to hold them on but may prevent the initial movement.

    I believe there is a coke can bodge also

    Premier Icon sillyoldman
    Subscriber

    The pinch bolts being correctly AND EVENLY tightened is what keeps your crank on – not the preload cap. It wouldn’t be made of plastic if it was meant to do anything but provide initial preload on the BB.

    LoCo
    Member

    Loco I’d love a new crankset- everythings overpriced at the mo

    Get something second hand then, or a replacement l/h arm that is just going to keep coming loose or fail at a key moment

    hora
    Member

    Good point loco. If I can find (any) lefthand 170mm crank arms (will look).

    The spline on the axle from memory is fine (as its hardened steel).

    fozzybear
    Member

    Hora.
    We followed a guy down the final decent at Blade.
    He had XT cranks with the same issue (and he lost a bolt too somehow!)
    He was bloody lucky he didn’t come a cropper, he dropped the crank arm mid roll of on a stone drop and just saved it.

    Had it been 2 seconds later he would have been in A&E.

    hora
    Member

    Fozzy I was riding down screaming mile here in the Peaks at a fair pace and I thought the pins on my left pedal must be time to be replaced/renewed…didn’t realise that the crank was showing 1 inch of axle…

    On the final cheeky and steep descent I had to kink my left foot ‘in’ to ensure the crank stayed on. just pedalling along wound it off.

    I reckon if it had come off on screaming mile I’d have gone straight down onto the bars/to the left and a broken arm/leg etc. Still. It didn’t happen πŸ˜€

    fozzybear
    Member

    It’s been nearly of those things..

    hora
    Member

    Ok old HT2 Deore crank arm fits. Repaired πŸ˜€

    Premier Icon JoeG
    Subscriber

    Is the new crank arm 180 mm by any chance? πŸ˜‰

    If not, you had a golden opportunity to try a 180 mm one without committing to a whole crankset! 😑

    That would have been a good thread, I think. πŸ˜›

    hora
    Member

    Knackered hips though πŸ˜‰

    Premier Icon mikewsmith
    Subscriber

    I had one of the early HTII’s come off on me while in mid air over a flight of steps one evening. 10 years later I still have no feeling in the skin where I landed.

    Make sure it’s not going to come off.

    hora
    Member

    Make sure it’s not going to come off.

    This has been playing in my mind over night. I love botching things but not things that are safety-critical.

    Premier Icon amedias
    Subscriber

    I’m glad that the introduction of splined axles solved all those wobbly falling off crank problems we used to have with square taper πŸ˜‰

    gonzy
    Member

    you want some cranks too? πŸ˜‰

Viewing 23 posts - 1 through 23 (of 23 total)

The topic ‘Non-driveside crank falling off (not running enough thread to lock)-Question’ is closed to new replies.