How to Change a Crank Bearing on a BMX
- 1). Position the bike on a flat, level surface. You may find it helpful to have someone hold it upright while you release the locking nuts on the bottom bracket. They often require a degree of force that can move the bike.
- 2). Use the crescent wrench to turn the locking nut that surrounds the arm of the crank counter-clockwise. Grip the opposite crank to provide the necessary leverage. Slide the nut away from the bottom bracket, toward the pedal, then do the same with the washer underneath.
- 3). Use a bottom bracket pin tool to get the bearing race off. The race is a tapered bolt that fits inside the bearing cup to hold the bearings tightly against the outer cup. The tool resembles a pair of tweezers with 90-degree hooks at the ends of the prongs. Push the hooks into the two holes on the back of the bearing race and rotate it counter-clockwise around the crank.
- 4). Slide the bearing race off the crank, which will reveal the bearing cups underneath. These curved bowls seat the bearings in a circle around the crank, supporting it as it rotates. Gently pry the cups out of the bottom bracket and replace with the new bearings. Replace the races, the washer and the locking nuts.
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