Bicycle Mechanics - unbolting bolt on crank arms.

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noxyce
07-01-11, 08:18 PM
I'm looking to unbolt the crank arms on my GT Idrive, but the bike shop loctited everything together. I'm just wondering if these bolts are right hand or left hand thread, or are the the same as the peddles right on right, left on left? Thanks.

oldbobcat
07-01-11, 08:26 PM
Both crank arm bolts are standard (lefty-loosey) threaded. After you remove the bolts you will need a crank arm extractor to remove the crank arms. See the Park Tool web site for instructions on removing and re-installing crank arms.
Jeff Wills
07-01-11, 08:30 PM
The bolts that hold on crankarms are right-hand thread. If they're on tight, count your blessings. Too-loose crank bolts will allow the crankarms to work loose, which ruins them.

FWIW: if you're going to take them off, you will probably also need a crankarm remover, like this: http://www.parktool.com/product/crank-puller-for-square-taper-cranks-ccp-22 . There's a couple variations, so it would be nice to know what kind of cranks are on your bike. Also, when you put them back on, you'll want to torque them down properly- they should get 25 to 35 foot-pounds of torque. (See http://www.parktool.com/blog/repair-help/torque-specifications-and-concepts .) You can't do that very well with a little socket or hex (Allen) wrench.

MudPie
07-02-11, 09:28 PM
Using a threadlocking compound is unnecessary on a bicycle. If the fastener is torqued properly, it will be fine without any thread locker. In my experience, the crank arm bolts need about 30 ft-lb of installation torque (imagine a 30 lb weight hanging off a 1 foot wrench). And you'll need more than that to remove it. It's quite a bit of force, and I usually use automotive type wrenches to remove. You won't be able to remove with a multi-tool.

When you reinstall the bolt, grease the threads, to avoid sticking/corrosion in the future. And use of torque wrench is highly encouraged especially if you have square taper bottom bracket to crank arm interface. As Jeff pointed out, loose crankbolts is often a prelude to buying a new crank arms.

Also, you might want to wear gloves, so your skin doesn't meet the mean teeth of the chain ring when the bolt finally gives.