Bottom Bracket Model
Bottom bracket model tells you the Crank Type:
- BB-UN100 square taper cartridge
- BB UN26 Square taper
- BB-MT500-PA Hollowtech II
- SM-BB52 Hollowtech II
- RS500 Hollowtech II Sora/ Gravel bike
- ES300 Octalink
HOW TO ORDER SPARES:
- If you are trying to replace a standard square taper BB, you must specify the shell width and spindle length. Eg: 68mm and 127. The Shimano BB-UN55 is very common and comes in 3 widths and 7 spindle lengths.
- if you are trying to replace Hollowtech you don't need to know anything. The hollow spindle is part of the crank, not the BB
- if you are replacing the whole crank system with another, you need to ensure the existing chainline is maintained. Eg: If you replace a UN-55 with HollowTech, you need some idea of what the chainline will be.