BMX Bottom Brackets Are the Core of Your BMX

On a BMX bike, you will find the bottom bracket installed in the frame where the crank arms meet each other. This part of the bike frame is called the bottom bracket shell. The main components are 2 bearings and spacers, and their purpose is to allow the rider to spin the pedals freely to get speed. The parts are extra strong and sturdy as they need to withstand a lot of pressure that is created by aggressive pedaling.

The Different Types of BMX Bottom Brackets

The four main types are - American bottom bracket (51 mm), mid bottom bracket (41 mm), Spanish bottom bracket (37 mm) and euro bottom bracket (35 mm threaded). They all have different sizes, and the measurements here are referring to the outer diameter of the bearing required to fit your frame.

American bottom brackets are the oldest type and have the largest diameter. They come with sealed bearings or open bearings that sit in cups. Mid bottom brackets are found on most BMX bikes these days, as they are simple to install and sit plushly in the frame. Spanish bottom brackets are small and lightweight, giving them a clean look. They are also pressed into the frame rather than threaded. Euro bottom brackets are commonly found on race BMX bikes. They are threaded into the frame with the bearings sitting in cups.

What Size Bottom Bracket Do I Need BMX?

Along with the type of bottom bracket, it’s important to have the right size bottom bracket so that it fits your crank axle. The different inner diameters of bottom brackets are 19 mm, 22 mm and 24 mm. These measurements refer to the size of the spindle that goes through the bearing. 19 mm axles are the most common, and nearly all brands have models of this size. 22 mm and 24 mm axles are thicker and stronger than the 19 mm and, in most cases, have no additional weight.

So, if you’re still unsure what bottom bracket you need, then the bottom line is to make sure that both the style and spindle size are compatible with your existing setup. For example, if your frame supports a euro bottom bracket and your cranks have a 22 mm axle, then you will need a euro 22 mm bottom bracket.

If you are also looking for a crankset to go with your new bottom bracket, then check out BMX Cranksets.