Bottom Bracket Sizes

When it comes to bottom brackets, there are a few key things to consider. First, there are three spindle sizes to choose from: 19mm, 22mm, and occasionally 24mm. Additionally, there are four different types of bottom brackets: American, Euro (threaded), Mid, and Spanish.

Each type of bottom bracket has a different outer diameter, with American measuring at 51mm, Spanish at 37mm, Mid at 41.275mm (or 1 5/8 inch), and Euro being threaded. For example, if your frame's bottom bracket measures 37mm and your spindle is 22mm, you'll need a 22mm Spanish bottom bracket.

 

Bottom bracket	Outer diameter
American	51mm
Spanish	37mm
Mid	41,275mm (1 5/8 inch)
Euro	Threaded

When installing a bottom bracket, there are a few important tips to keep in mind. First, always use grease to ensure proper lubrication. Additionally, make sure the bearings go in straight and don't forget the spacer between them. For press fit bottom brackets, a rubber hammer can be used, but be sure to place a piece of wood between the hammer and the bearing to prevent damage.

Finally, if you're working with a threaded Euro bottom bracket, remember that the left bearing needs to be screwed in counter clockwise. Look for markings on the bearings themselves that indicate which side of the frame they need to be inserted on, labeled "L" and "R". And most importantly, make sure to screw the bearing in straight to avoid any damage or misalignment.