If you want to buy a bottom bracket for BMX but don’t know which one to choose, this article will help you.

1) You must find out the outer diameter of the bearing;

2) You must find out the diameter of the crank axle;

MID BB:

External diameter bearing is 46mm

SPANISH BB:

External diameter bearing is 42mm

The inner diameter of the bottom brackes is the size of crank axel, they are:

• 19mm
• 22mm
• 24mm

Now we can draw the following conclusion:

• If we have an outer diameter of 46 mm and crank axel of 19 mm, we need a MID 19
• If we have an outer diameter of 46 mm and crank axel of 22 mm, we need a MID 22
• If we have an outer diameter of 46 mm and crank axel of 24 mm, we need a MID 24
• If we have an outer diameter of 42 mm and crank axel of 19 mm, we need a SPANISH 19
• If we have an outer diameter of 42 mm crank axel of 22 mm, we need a SPANISH 22
• If we have an outer diameter of 42 mm crank axel of 24 mm, we need a SPANISH 24 - but these are not the case.