Crankshaft fell off, and loose again :/

Antilles

Hi,

got a bike six or seven weeks ago. Everything was grand until about thee weeks in, when I started feeling a "wobble" on the left pedal. When I looked at it, I saw that the left "crank arm" (I think that's what its called - its the bit that connects the place you put your foot to the circle bit in the frame) was about half an inch out from where it connects to the "crank" (the circle bit in the frame? Sorry if I'm not using the right terms, I'm a total newbie when it comes to bikes).

I was pretty sure it used to be flush against the crank, but couldn't see any way to screw it back in closer. The day after I noticed this, I was cycling to work and the left crankshaft just -fell off the bike-.

I brought it back to the store, they "ordered in a part" to repair it, and a week later I had it back in working order.

Now this morning, I cycled to the train station and felt the exact same wobble. Checked where the crankshaft meets the crank and again, about half an inch out. I havent had any crashes, or come off the bike at all. Never threw it on the ground or did anything except cycle it to and from work. I don't want the thing to fall off again in traffic, so I'm thinking of bringing it back to the store -again- before that happens.

Has anybody else had this happen to them? Is it common? I've never even heard of the entire crankshaft just falling off before. Is there a way for me to repair it without being without my bike for a week?

davidsatelle100

Bring it back and be looking for at least a loan of a bike for the week if not a new bike

kenmc

happened to me mountainbiking recently, I hadn't tightened the crank bolt sufficiently after I rebuilt the bike, nor used threadlock. El Tonto also had his crank come loose on a saturday spin. So yes it happens - but it shouldn't happen twice in a row like that.
What sort of bike is it, and what shop repaired it??

blorg

Happened to me too, on two different bikes, soon after I had got them. First time was up on Sally Gap, on my own, with the night closing in (fun times.)

I would be worried that if it has happened to you twice the threads might be damaged- either way the bike shop should sort it out. If it has happened twice possibly some threads have been damaged and will need replacing. Should be perfectly fixable though, bike shouldn't need replacing.

Chips Lovell

If I had to guess, I'd say it's one of two things:

a. They're crap cranks. What's the make and model?

or

b. The shop has been installing them improperly.

kenmc wrote: »

El Tonto also had his crank come loose on a saturday spin.

They came loose because the head of one of the fixing bolts was damaged and you couldn't torque it down since the wrench wouldn't grip. I was using those cranks because I'd broken another set and was waiting for a replacement. I figured having to stop and tighten my crank bolts once or twice on a spin was better than not riding at all.

Raam

el tonto wrote: »

They came loose because the head of one of the fixing bolts was damaged and you couldn't torque it down since the wrench wouldn't grip. I was using those cranks because I'd broken another set and was waiting for a replacement. I figured having to stop and tighten my crank bolts once or twice on a spin was better than not riding at all.

So you're the problem?

Chips Lovell

Raam wrote: »

So you're the problem?

Yup

bealbocht

yup...

had this with a pedal arm before..

with some alloys, they are strong when the nut is tight.. but with the nut is loose... and the arm can move about.. it loses its shape/or errodes/ becomes fcuked very quickly and cannot be tightened again.

must be replaced..!!

CheGuedara

bealbocht wrote: »

yup...

had this with a pedal arm before..

with some alloys, they are strong when the nut is tight.. but with the nut is loose... and the arm can move about.. it loses its shape/or errodes/ becomes fcuked very quickly and cannot be tightened again.

must be replaced..!!

Yup, same thing here on one of my first bikes. Arm wasn't tightened properly first day, loosened through use wearing both the inside of the crank and the taper of the b.b. axle . Only solution was new b.b. and crank arm in the end

dave2pvd

Ooo: lots of Octalink-esque issues coming up on this thread.

The 1st Shimano Octalink (105, Ultegra, Dura-Ace) crankarms have shallow tapered splines that need to be installed and torqued perfectly to stay on. Many an owner and shop mechanic have messed Octalink up.

My TT bike is 9-speed, with an old Ultegra crankset (Octalink 1.0). I apply some Loctite Blue to the crank nut threads, just in case. Oh - I also use a torque spanner.

tomc

Saw someone attempting to cycle to Bikez (Hollingsworth) in templeogue with exactly this issue last weekend!!!! Think it was a Dawes.

TomC