Aargh... loose cranks!

[Diamant_Don]

Hi Guys,

Following my last thread, I've fixed the headset on my Diamant, removed the plastic tat, and the bike was running smoothly... until this morning's commute that is, when the non-drive side crank suddenly decided to become really loose (and if I hadn't stopped would have fallen off). It's a Shimano Exage 500EX set, with simple bolt fixings by the look of it.

A couple of questions (warning: imbecile home mechanic content):

• Do I just need to tighten up the non-drive side crank with a torque wrench?
  If so, how much wrenching is required? I'm scared of breaking the thing!
  Why's it suddenly come loose? Will it happen again?

Cheers!

 

[hamster]

Firstly, cranks bolts need to be tightened after about 100 miles after fitting. The crank always settles a bit.

Yes, a torque wrench is perfect for the job. 35-45Nm is the sort of level most recommend.

It may come loose again if you have damaged the tapers. If you are lucky, you have got away with it...

 

[Diamant_Don]

Thanks a million hamster! Good to know it's a common thing... I was beginning to think evil thoughts about the guy who restored it and sold it to me!

Now just got to get my hands on a suitable torque wrench!

 

[Ian Raleigh]

If the cranks do come loose again! Stop riding it as the axle will surly damage the alloy tapers.

After tightening the cranks and you feel un-settled that the cranks will come loose
again take the correct tools with you just in case they do come loose again.

My drive-side crank was always coming loose so I washed out the axle & bolt in thinners
and applied a tiny drop of thread lock onto the bolt thread, never came loose again,
though never over do it with thread lock as they could never come off again.

 

[Diamant_Don]

Thanks Ian... I was going to try riding the bike home carefully, with the crank bolt hand tightened :facepalm: , but it sounds like I could do some serious damage.

 

[Ian Raleigh]

You could always take off the loose crank arm and pedal with one crank!

I did exactly that on a 25 mile TT race and nine miles from the finish I heard
something drop off the bike and looked about and couldn't see anything,
then my left crank came straight off with my foot still attached..lol

Wanting to finish the TT! I stopped and un-clipped my shoe and held
the crank on my bars and finished the 25 mile TT in about 1hr 3min's.

 

[Diamant_Don]

I did exactly that on a 25 mile TT race and nine miles from the finish I heard
something drop off the bike and looked about and couldn't see anything,
then my left crank came straight off with my foot still attached..lol

:shock:

Retrobikers are obviously a tough and ingenious lot... and I have much to learn!

 

[Diamant_Don]

Cheers everyone. In the end I took the bike to my LBS, who was pretty scathing about the fact that the guy who restored it had apparently omitted the washers when reattaching the cranks and had just screwed in the bolts... :shock: I've ridden the bike 3 or 4 miles and so far the cranks still seem to be attached, so hoping for the best that the fix holds... Thanks for assistance, all!

 

[Ian Raleigh]

No washers! What an arse the previous owner was or maybe he didn't realise or forgot them.

 

[Diamant_Don]

Yeah, the LBS guy said the same - after he'd accused me (several times) of probably botching the job myself and refusing to admit it. Turns out there's a few other things that will eventually need fixing, but then the guy (let's call him arse) wasn't a professional, just some old guy tinkering for a hobby in some sad washer-less world!

Thanks again Ian - is there a point at which I can relax, not worrying if the cranks are going to come loose again - say 50 miles or so?