Aluminum Vs. Chromoly BMX Bike Frames

BMX bicycle frames are commonly manufactured with aluminum or chromoly steel tubes.

BMX is a misnomer often used to define any 20-inch wheel bicycle. BMX actually stands for bicycle motocross, a recent addition to the Olympic sports pantheon. Bicycle motocross frames are commonly made of chromoly steel and aircraft grade aluminum tube sets. Exotic expensive titanium or carbon fiber frames are uncommon but available.

BMX Bike Frames

BMX bicycle frames are primarily assembled in China or Taiwan, but several companies still manufacture high-quality BMX frames in the United States, according to online BMX guide American Made BMX. S&M American Bicycle Co. and Standard Byke Co. construct chromoly BMX frames. Clayborn BMX, Direct Link BMX, Inc. and Redman Bicycle Motocross build aluminum BMX frames. BMX Sherpa, an online BMX resource, lists several companies, such as Diamondback and Felt, manufacturing frames outside the United States as well.

Aluminum Tubing

Common aluminum tubes used in bicycle construction are aircraft grade 6061-T6 aluminum tubes with different butts--thicknesses--of tube walls. Some manufacturers use specially formed tube sets or exotic aluminum alloys, such as scandium. Aluminum BMX tubes commonly weigh less than chromoly BMX tubes, which often results in lighter overall frame weight as well.

Chromoly Tubing

Common steel tube sets used in BMX frames are 4130 chromoly steel. The number 4130 refers to the alloy mixture of chromium and molybdenum added to common steel as both a strengthener and a weight reducer. Welding steel BMX frames is often less costly and easier than aluminum and produces a frame of equal strength with little weight gain.

Aluminum BMX Frames

Aluminum BMX frames are designed for the rigors of BMX racing and generally look overbuilt compared to chromoly frames. Aluminum tubing is larger in diameter than steel tubing and is often formed into box or diamond shapes for stiffness when utilized for BMX frame construction. Alumnium BMX frames are designed strictly for BMX riding and are not designed for street or park use.

Chromoly BMX Frames

Chromoly BMX frames are also designed for bicycle motocross use and are not constructed for the dangers of freestyle riding, though, typically, steel BMX frames hold up to abusive street and park riding better than aluminum. Chromoly BMX frames are what started BMX racing in the 1970s, and many companies still manufacture tradition-tested quality chromoly frames.

References

• American Made BMX
• Bicycle Sherpa: BMX Bikes