Mountain Bike Crank Coming Loose

You will have no choice but to replace it.

Mountain bike crank coming loose. If yours are held on by nuts in the sides of the crank arms you can also remove the crank arms by riding the bike but you must do this very carefully to avoid damaging the crank arms. This will make the noise when you pedal. It comprises a series of nuts and bolts and function by pulling the crank from the engaged axle. Use a park bbt 9 22 18 or similar tool to check the tightness of the bearing cups in the frame a loose cup will generate a creaking noise under power.

Cottered cranks are often found on older bicycles and you can identify these from the cotter bolts that thread through the top of the crank arm. Using a drop of loctite on the chainring bolts will prevent them from coming loose in the future. These cranks and bolts are usually made out of aluminum because of its lighter and more stable performance. A cotterless crank has a hex bolt in the center top of the crank arm.

If this doesn t work the crank loosens after a short period of time or the bolt is missing there are more drastic measures. You can tell whether you have this kind if the parts of the bottom bracket that screw into the frame are quite wide 1cm or wider. Complicating matters further there are several types of crank arm fixings out there. The most recent types of bottom brackets and crank arms have external bearings.

You can try locktite but i ve had no success with that either. A cotterless crank has a hex bolt in the center top of the crank arm. Somehow this damage causes the crank arm to wiggle enough to unscrew the nut little by little until it just falls off again. Bicycles have two types of cranks cotterless and cottered.

When the crank arm is loose and you pedal with it you damage the four corners of it s socket that rest in the axle. Before sliding in the crank double check the bottom bracket bearings as they can come loose.