How to Replace Sealed Bearings in Bottom Brackets
- 1). Check the wear on a sealed bearing bottom bracket by removing the chain and spinning the crank. Worn bearings will make a noticeable grinding noise and cause vibration that can be felt through the frame.
- 2). Put the bicycle into a repair stand and remove both cranks. This requires a crank puller, or in some cases, nothing more than an Allen wrench if the cranks have a self-extracting mechanism. Remove the retaining bolt and thread the crank puller into the arm clockwise. Be certain that any washers are removed before inserting the puller. Tighten the body in place, then turn the extracting bolt to remove the arm.
- 3). Insert the bottom bracket tool in the steel side of the bottom bracket cartridge. Often one side is steel and the other is aluminum or plastic. These tools are splined to fit internally on the bottom bracket cartridge, but in some cases, the cartridge splines are very shallow. Use a crank retaining bolt, or if the spindle is hollow, a quick release lever, to hold the tool in place so it cannot come out. Turn the cartridge out of the bottom bracket with a large adjustable wrench, a 1/2-inch socket wrench or breaker bar. Remove the opposite side retaining ring with the bottom bracket tool also.
- 4). Clean the bottom bracket with a rag and solvent. Remove all grease and dirt from the threads. Inspect the bottom bracket inside and out for any cracks. Apply threadlocker to the new cartridge threads -- or anti-seize compound for an aluminum or titanium frame -- and install the cartridge in the bottom bracket. Most cartridges are marked with an L or an R. L is a left hand cartridge that installs clockwise in the left side of the bottom bracket. An R cartridge installs by turning counter-clockwise in the right side. Install the removable ring on the other side and torque it to 360 inch-pounds. That's very tight. Install the cranks.
