Loose Crank Arm Problem

You have managed to fuck it entirely by the looks of it... usually I would say you can bodge it with Aradite rapid and a huge amount of HTFU on doing the bolt up, if you are a poor student but this is far beyound bodging IMO.

On my way to work this morning I suddenly felt a wobble in the left crank arm then wahey the whole thing fell off. Shat myself a bit, put the arm back on and noticed that the two bolts that hold the arm onto the spindle were loose. Have tightened them to within an inch of their life and have yet to test it out (am at work.....working hard).

Just wanted to know if anyones had any similar problems and if its potentially something serious?

Its a Subrosa Malum 2009 btw.

Cheers

I saw a guy this morning at the side of the road who had snapped his crank arm in half...shocking start to the day. Pedal clean off under the shoe!

I've had the whole arm come loose before, so also tightened it. Been OK since. That, plus a clean up of the bracket - not alot more you can do I would guess?

clean grease and tighten
the cycling mantra

Fingers Crossed for my ride home....

Still, was half expecting a 'YOU NEED TO REPLACE THE BOTTOM BRACKET AND CRANKSET' message so thats a plus.

As said, clean and grease. Hopefully you're not going to need a new bb/crankset, but if the crank was loose for a decent period of time while you were riding it then it may have worn it out. You should find out if it's still ok over the next few weeks but if it keeps coming loose then you'll need to get an new one.

square taper? if so you'll probably need a new crank arm, but the bb should be fine

Sounds like a Hollowetech2 style thing with 2 bolts holding the arm on.

as matty said you problaby need a new crank arm.

i read on several fora's that it works to put some teflon (plumber) tape around your taper and then put you crank arm back on.

make's sense i used this method on my headset and plotted headtube. never had a problem again.

clean grease and tighten
the cycling mantra

Do NOT grease your crank arm/axle

Bad, bad idea.

Squeak squeak creak creak?

You normally want to grease metal so that nothing seizes, only, you kind of want your axle and your crank to fall in love and stay together, not to have something come between them.

Ah, yes the true love bond of crank plus axle. Though, you don't want to have to divorce it with an angle grinder when the crank puller pulls the thread out of the crank arm.

^
Bitter experience that.

Happened to me before. Check the taper on your crank arm.. if it looks mashed up you'll need to replace it (but probably not)
I say a little bit of grease on your axle and loctite your bolts.

wharry your joking right?

no to locktight on crank bolts.
if you have to tighten it so much that you are damaging stuff then I'd say your tapers are fubared.

clean both surfaces very well, you want the lightest smear (almost a streak) of something greasy on the tapers, then refit bolt and tighten up (bolt + threads should be cleaned out too), f you don't have a torque wrench (you should have one of these really) to get to mftrs specs then bend over the bike, wrench at 3oclock, crank at 90clock, and slowly put your weight via your shoulders onto it, there will be a point where the amount of force req'd will suddenly increase, thats where you want to stop to avoid stretching things.
do not put thread locker on crank bolts. a few months of british weather (and teh correct torque) will ensure that bolt stays there.

I saw a guy this morning at the side of the road who had snapped his crank arm in half...shocking start to the day. Pedal clean off under the shoe!

I've had the whole arm come loose before, so also tightened it. Been OK since. That, plus a clean up of the bracket - not alot more you can do I would guess?

Was he a courier on a blue low-pro Eddy Merckx?

Do NOT grease your crank arm/axle

Bad, bad idea.

Seriously?

as damo said, squeaky squeak squeak.

merest smear of grease on the taper is what I go by. I'm not a mechanic though.

This has happened to me twice - the crank snapped in the middle

merest smear of grease on the taper is what I go by. I'm not a mechanic though.

If only there was a mechanic on this page, who had offered up advice about this very topic.

better than that, we are forum mechanics, between us we are better than any shop mechanic could ever be.

;)

If only there was a mechanic on this page, who had offered up advice about this very topic.

that's why i'm confused

Me too, ive always been under the impression that *lightly *greasing your BB axle was the norm?