BMX bikes are built for racing or freestyle riding. Racing BMX bikes are lightweight, designed for speed and stability, while freestyle BMX bikes are sturdier, with thicker frames and tires, designed for maneuverability while doing jumps and tricks. Most BMX bikes have 20" tires, while the larger frames may use 24" tires - also known as cruiser class BMX bikes. When figuring out frame size, only the rider's height is important. This calculator will recommend a BMX frame size based on your height measurement.