BMX Bottom Brackets

The Essence of Your BMX: BMX Bottom Brackets

In a BMX bike, the bottom bracket is located within the frame at the convergence of the crank arms. This segment of the bike frame is known as the bottom bracket shell. The principal components include two bearings and spacers, designed to enable the cyclist to rotate the pedals with ease for speed. These parts are exceptionally robust and durable, as they must endure the immense pressure produced by vigorous pedalling.

Varieties of BMX Bottom Brackets

The four primary varieties include the American bottom bracket (51 mm), mid bottom bracket (41 mm), Spanish bottom bracket (37 mm), and euro bottom bracket (35 mm threaded). These types each feature unique dimensions, with the specified measurements indicating the outer diameter of the bearing needed to fit your frame.

American bottom brackets are the earliest form, featuring the largest diameter. They are available with either sealed bearings or open bearings that rest in cups. Most contemporary BMX bikes are equipped with mid bottom brackets, as they are straightforward to install and fit snugly within the frame. Spanish bottom brackets are compact and lightweight, offering a neat appearance, and are pressed into the frame rather than threaded. Euro bottom brackets are typically seen on race BMX bikes, where they are threaded into the frame with bearings housed in cups.

Determining the Appropriate Bottom Bracket Size for BMX

Choosing the correct bottom bracket size is crucial alongside the type, ensuring it aligns with your crank axle. The various inner diameters for bottom brackets are 19 mm, 22 mm, and 24 mm. These figures pertain to the spindle size that passes through the bearing, with 19 mm axles being the prevalent choice. Virtually all brands manufacture models in this size. Axles measuring 22 mm and 24 mm are thicker and more robust than the 19 mm, often without added weight.

If uncertainty persists about the required bottom bracket, the essential point is to confirm that both the style and spindle size are compatible with your current setup. For instance, if your frame accommodates a euro bottom bracket and your cranks have a 22 mm axle, a euro 22 mm bottom bracket will be necessary.

Should you also require a crankset to complement your new bottom bracket, consider viewing BMX Cranksets.