I have asked this before but still not resolved the issue, when i am out my crank arm just keeps working loose and faling off, its the left side, but it back on as soon as on a bad uphill it falls off. This may sound daft but I have rode the bike for the last 8 months no problems, buy a pair of Sam Hill Monster fivetens and it starts. What have i done so far.

Bought new crankset Xt fitted that same problem, had it at 2 bike shops they cant find a problem, someone said remove the black spacer on the top that is between the allen key bolts, still same problem, this is run with a hope bottom bracket. If anyone can help it would be much appreciated, as i hve just got back from a ride that was spoilt by this happening again. 🙁

you have the preload cap done up yeah? and the allen key bolts done up sufficiently tight?

The plastic 'hook' on the non drive crank arm should atleast stop it from coming off….odd…sorry just ruling out the simple things, some1 of authority will be along shortly!

some1 of authority will be along shortly!

sorry, no. Just me

I lost the LHS crank on a HTII chainset once. The bolts, IIRC, are supposed to be done right up to bastard-tight (but check this with instructions) and should be done in tandem rather than one after the other [- hang on, a tandem is one after the other ! (I mean don't do one all the way & then the other, do 'em piecemeal)]

I grease the bolt threads but guess you could use threadlock (not super-hard type) instead if it's them that are slipping. Similarly, maybe try something like carbon assembly paste on the axle splines rather than grease (I have never done this and suppose it could be disastrous but I'd try it if mine kept falling off)

Are you certain you haven't mashed the splines somehow? (though would have to be on 2 chainsets which seems a bit unlikely)

some1 of authority will be along shortly!

No just me… you said piecemeal, are you 98? 😉

No idea really, have you tried it with the XT BB? I got one you can borrow to try, but to be honest I cant see it making any difference.

you said piecemeal, are you 98?

I didn't fight 2 wars to put up with this crap from you laddie !

what bb type are you using? ht11?

you had a crankset and the crank fell off.
then a different crankset and the crank fell off that one too.

(whoever suggested this

someone said remove the black spacer on the top that is between the allen key bolts

is a nidiot)

It's unlikely (but possible) to be two faulty in the same way, so you should look at other components in that area.

it is most likely a problem with the B/B if you haven't changed that.

The little black spacer thing? The one that pivots on one of the pinch bolts and clips onto the other one?

Put the little black spacer thing back in, it's useful, and here's why:

The black spacer is not a spacer at all, but a guide. You might notice that it's got a little metal point sticking out of it. That metal point should fit into the hole on the axle when the LH crank arm is on in the correct position and, impotantly, ONLY when the LH crank arm is in the correct position. If the black spacer can't pivot into place easily (after you've done up the preload cap and before torqueing the pinch bolts) then something is wrong somewhere.

Things to check:

BB spacers – definitely got the right number of spacers of the right thickness in place for your BB shell width?

Preload cap – this doesn't hold the crank arm on, it just, well, preloads the bearings a bit. Don't do this up tight in the hope it will hold your cranks together. Just use the little tool to do it up finger-tightish. The crank is held on by the…

Pinch bolts – someone mentioned doing these up "barsteward-tight" which, sorry to be a stickler, is just wrong. Their advice to RTFM is good though. I don't follow EVERY torque guideline but manufacturers don't just pluck numbers out of thin air and in this case Shimano's numbers sould be followed. Torque the pinch bolts to the recommended torque setting.

It might be worth trying a different BB, just to see if that makes a difference, but I have a feeling that if the LH crank arm has come off once the splines will be shot and it'll never sit properly again.

what they sadi have you used spacers on 73 mm BB or is it a roadie BB that you have used and the lock pin thingy between the bolts cannot engage in the hole. Only way I can see it slipping off is if this is not in place/worn as it effectively locks it in place.

Wouldnt make any difference to it falling off wether it has the right spacers or not, if you dont have enough spacers you just get float on the axle and you will never get the front mech to work right (as the cranks move side to side), but it wont cause the arm to drop off.

If you dont have a standard shimano BB I got one I can lend you to try out to see if we can eliminate your Hope BB as the culprit. e-mail in profile.

possibly to many spacers? not allowing enough of the crank arm on to the axle?

i was having issues with my drive side crank continuously working loose not matter now much i tighten up my crankset.

there is more on the above topic at http://www.singletrackworld.com/forum/topic/raceface-cranks-wobble-issue

in the end i had a spare set of cranks that i changed to that solved the problem.

tinsy if you have a 73 mm BB and you add the three spacers then you dont have enough space left to fit the crank on properly and enegage with the pin and thereefore it falls off. You are correct if you have too few spacers yo would just get float but not if you have made the BB too wide to actually fit the drive arm

Its been to 2 bike shops surely one would have spotted something like that anyhow, but I do get your point junkyard.

I would imagine there is something not right with the Hope BB but then thats me just guessing!!!

I have a standard XT BB he can try and a good pair of XT arms too, if pendlechris pays the postage, just to try though as I want to keep them as spares.