The primary parts to replace when customizing a BMX bike are the frame, rims and cranks. Custom tires are also a popular way to enhance BMX activities.
Most bike frames are made of high-tensile steel, chromium-molybdenum steel or reinforced aluminum. Steel frames are typically more durable and less expensive, while aluminum frames are more expensive and feature a lighter weight that improves agility. Steel frames are typically used for basic dirt jumping and freestyle riding, while aluminum frames are typically used for racing. Some dirt jumping and freestyle professionals use aluminum frames, but beginners should avoid them because they are easier to damage.
The major considerations for choosing cranks are strength, weight, girth and ease of maintenance. Trick bikes generally use machined aluminum or chrome cranks, while racing bikes commonly use aluminum or titanium cranks. Cranks can be customized to the rider's weight, height and style.
Mag rims or 48-spoke rims are better for freestyle riding, while 32-spoke aluminum rims are better for racing due to their smaller weight. Jumping requires 48-spoke rims or rims with 36 heavy-duty 13-gauge spokes. Slick tires perform better on ramps, knobby tread tires are best for tricks, and multi-tread tires are best for freestyle riding.