A few things cause the crank arms on your bike to creak persistently. Cranks arms attach to spindles on each end of the bottom bracket and can creak if the attachment is loose or needs grease. Another cause of noisy crank arms is damage that you may not be able to find without removing the arm using a special tool. You obtain the tool and a new crank arm at a bike shop. An inspection tells you what’s needed to fix a creaky crank arm on your bike.
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Mount your bicycle on a stand or turn it over onto the seat and handlebars. You can put a piece of carpet or a blanket down first to prevent scratches, if necessary.
Rotate the pedals by hand, if necessary, and listen closely to establish which arm is creaking. Grip the end of the noisy arm above the pedal and manipulate it in different directions to determine if the arm is loose.
Remove the dust cap from the base of the crank arm to expose the attachment bolt. Depending on the style of cap, you pull it off by hand or carefully pry it off with the tip of a small flat screwdriver.
Stabilize the crank arm with one hand. Depending on the type, tighten the crank bolt clockwise with an 8-mm socket wrench or 8-mm hex wrench. Take a short test ride. Return to the work area and proceed if tightening the bolt did not eliminate creaking.
Mount the bike on the stand or balance it on the seat and handlebars. Hold the noisy crank arm stable with one hand. Loosen and remove the crank bolt using the 8-mm socket or hex wrench.
Servicing and Replacement
Set up a crank puller tool to remove the creaking crank arm. Unscrew the fitting at the head of the puller by hand until it is even with the end of the steel pin. Screw the fitting into the hole where the crank bolt was removed by hand and tighten the fitting until it stops.
Attach an adjustable wrench on the outer end of the puller. Hold the handle of the wrench steady with one hand as you rotate the handle of the crank puller clockwise. Continue to rotate the handle of the puller to remove the crank arm.
Inspect the base of the crank arm where it attaches to the bottom bracket. Look for line cracks at the inner and outer surfaces of the base that tell you the arm must be replaced. Obtain a replacement arm or proceed to the next step.
Apply a modest amount of multipurpose grease on the outer face of the bottom bracket. Wipe any residual grease off painted surfaces on the bike frame with a shop rag. Position the base of the crank arm at the spindle so the arm points in the opposite direction of the crank arm on the side of the bike. Push the crank arm onto the spindle by hand.
Screw the crank bolt into the base of the arm by hand. Hold the arm steady with one hand and tighten the bolt securely with the socket or hex wrench. Push the dust cap on by hand.