BMX Bottom Brackets

BMX Bottom Brackets: The Heart of Your BMX

Within a BMX bike, the bottom bracket is situated in the frame where the crank arms converge. Known as the bottom bracket shell, this area houses 2 bearings and spacers. These elements allow the pedals to rotate freely, aiding the rider in gaining speed. Given the significant pressure from intense pedaling, these components are robust and resilient.

Varieties of BMX Bottom Brackets

There are four primary types: American bottom bracket (51 mm), mid bottom bracket (41 mm), Spanish bottom bracket (37 mm), and euro bottom bracket (35 mm threaded). The varying sizes here refer to the outer diameter of the bearing necessary to fit your frame.

American bottom brackets, the most traditional type, feature the largest diameter. They include either sealed or open bearings encased in cups. Nowadays, mid bottom brackets are prevalent on most BMX bikes due to their straightforward installation and snug fit in the frame. Spanish bottom brackets, being compact and light, offer a sleek appearance and are pressed, not screwed, into the frame. Euro bottom brackets are typical on race BMX bikes, and they are screwed into the frame with the bearings positioned in cups.

Determining the Correct Size BMX Bottom Bracket

Aside from the type, it is crucial to select the right size bottom bracket to suit your crank axle. Inner diameters of bottom brackets differ as 19 mm, 22 mm, and 24 mm, referring to the spindle size that passes through the bearing. The 19 mm axles are widely common, with nearly all brands offering this size. Thicker and sturdier than the 19 mm axles, the 22 mm and 24 mm usually add no extra weight.

Should you remain uncertain about the bottom bracket you require, ensure that both the style and spindle dimensions align with your current setup. For instance, if your frame accepts a euro bottom bracket and your crankset has a 22 mm axle, a euro 22 mm bottom bracket will be necessary.

If a crankset is also on your shopping list to accompany your new bottom bracket, do have a look at BMX Cranksets.