The crank set transfers the power of a rider to the back wheel. The two parts of the system are the bottom bracket and the cranks. This is how you install and remove a cartridge bottom bracket. First you take the nut or bolt off with a wrench. second you have to take the crank arm remover and make sure you don’t stripe the cranks out when you take them off. The next thing you have to do is take off the non drive side bottom bracket, then you take the drive side bottom bracket off but remember the drive side is reverse threaded. After you have done all of this you wipe the old grease off and put new grease on everything you took off that has threads. When your ready to put the bottom bracket on your make sure the drive side goes on the right side and install your left side as well. After that put your drive side crank on and make sure you put the other crank on the opposite you put your drive side on. Put the bolts back in that hold your crank on and torque it down to 35 to 40 new ton meters.