Loose Crank Arm Problem

ok thanks people - will buy some locktight and tighten it to buggery and see what happens

:)

well my allen key is about as long as its going to get i think :) - but ok ill try tightening as tight as i can

I tighten my monkey wrench on the allen key end for extra leverage.

stick a piece of pipe over your allen key for a better grip

Borrow a long handled ratchet or torque wrench and a hex driver to fit it.

you can put a ring spanner over the end of an allen key to get it 'beastman' tight
http://i463.photobucket.com/albums/qq354/rhordyk/13-nutremoval.jpg

shudders

shudders

just a tip, whether it's right to apply this is down to YOU

Better than fucking up the tapers on your cranks anyhoo.

Torque wrench would be better...

Torque wrench would be best...

This sort of job can only be done by someone with a really long tool. Most bicycle workshops employ just such a person.

Failing that, consider using a torque wrench.

My brother (the more mechanically minded of the family) visited recently, and commented on the overtightening of bolts in general.

"*if it wanted a fking thousand cting newtons putting on it. It would'nt have a fking piss small allen bolt on it. If you have to jump up and down on it like a tw*t, someones fked up!"*

Theres a lot of technical jargon in there, but I think see what he was getting at.

You need guns for this. Mine are for hire.

£5 a a crank.

Wam

Bam

Thankyou Mam!

Just need the right tool.

the one on the right or the one on the left

The one on the left looks to come from a university so small, its not afiliated to a city, or even a town, but a street.
I therfore choose right.

I got a fairly long-handled allen key (25cm?) with a rubber grip for about £3 from a bike shop. That, plus bodyweight over allen key / crank at "quarter past nine", plus a movement somewhat like giving CPR*, seems to do the trick.

• just the chest bit, I don't blow air into the headset
  

Hi,

since I already started looking for a replacement left crankarm, I took the left (supposedly broken one) off, looking for cracks or anything.

my problem in the first place was that after a little riding the left crank arm would start making annoying squeeky sounds and then ultimatly come lose. actually the bolt came loose.

talking to my bike dealer of choice he said if the bolt kept coming loose there might be a little crack in the crank. So I took it off and looked closely but found nothing!

Is there anything else that could cause this problem? the screw is new by the way....

I just can`t see why this keeps happening!!

thanks in advance for any help

sebastian

you need a new crank arm.

Basically, the crank is held onto the spindle by the pressure exerted by the bolt. This only works if the taper of the square hole in the crank accurately corresponds to the taper of the spindle.

If the bolt isn't tightened enough, or if it works itself loose (does happen every now and again), and the bike is pedalled, this deforms the tapers on the crank (because the metal is softer than the metal of the spindle.

Once this has happened, no matter how often you tighten the bolt it will work itself loose again, basically because the metal simply gives way and moves further up the spindle towards the bike frame.

Dunno which shop you went to but it's got nothing to do with anything being cracked. You want a new crank arm. left hand ones are fairly readily available, for this very reason. Any respectable bike shop should have them in stock and as long as you have the bolt the swap over procedure is fairly quick and painless.

Hope this helps.

helps alot and makes perfect sense....

I just liked the cranks as they were! :(

I`ll go get me new one tomorrow then! 165mm should also be available?

No worries!

165 will be harder to find than longer sizes. What sort of cranks do you currently have?

If you have campag/miche/anything with ISO, then the cycle surgery at spitalfields market have a left hand campy record pista crank arm in stock that was ordered in for a customer who never collected it.

Will probably set you back 30-50 quid though.

Otherwise best thing to do is try a few of the smaller independent shops.

Good luck!

i currently have a sugibo royal crank on there which I really really like and would love to keep...

but that seems fairly impossible!

and since I unfortunatly do not live in london, it will be even harder to find a decent replacement....

but thanks for your help

google is your friend.

and ebay. :)

I had this problem a year ago on a bike I bought second hand. Each time I tightened the crank it would quickly come loose. As I had some loctite in the garage I figured it was worth a try. Crank is still good and tight today [/stop typing one handed and release wooden table from other hand]

You have to keep the nut tight, Sooner or later they work loose. Loctite should stop it happening. However when mine worked itself loose. Very carefully filed out the rounded corners in the crank arm, kept the angles right. At this point the crank went way in too far towards the bearing. I then carefully cut a aluminium can so it made a collar to fit over the square spindle. It has to be good fit. Hammered the crank on with a soft hammer. Screwed the nut on with loctight and belted that too. Touch wood works a treat - but I check it weekly - don't like the crank arm dangling fom my leg when I'm cycling. An idea from Sheldon Brown.