Choosing a bicycle out of the thousands of designs and material variations can be daunting. Some differences between bikes are purely aesthetic, while others have a significant effect on performance. The material used in the bicycle's frame changes the weight, handling and durability, and should be one of the first considerations you make. The decision between the durability of steel and the light weight of aluminum depends on how you intend to use your bike.
Steel is one of the archetypal bicycle materials, and has been used since the earliest days of cycling. It's ductility makes it easily weldable for frame construction, and superior damping makes the bicycle comfortable for longer rides. A steel frame bike, when properly cared for, can perform admirably for decades. The most common steel used in modern bicycles is 4130 cromoly steel, which is lighter and stronger than carbon steel. Higher quality steel is more expensive, but 4130 cromoly is still affordable when compared to other materials like carbon fiber.
Lightening The Load
Aluminum is much less dense than steel and doesn't sacrifice stiffness, making it ideal for racing bikes that benefit from greater speed. An aluminum bike uses thicker walls in the tubing of the bike to make up for a reduction in durability. Unlike steel, aluminum can't be easily welded or re-bent once it's cast, making repairs to broken frames much more difficult. Still, aluminum's low density makes it an exceptional choice for a high-performance racing bike, and rivals carbon fiber as a material for a competitive frame.
Pros and Cons
Steel's longevity makes it a popular choice for riders who expect their bike to undergo a lot of punishment. Mountain bikers, touring cyclists and commuters have long lauded steel's reparability and strength, since bikes made with steel will usually outlive anything that gets thrown at them. Steel frames sacrifice weight for durability, which makes aluminum a superior alloy for competition. In the event of a crash, aluminum will usually crack, rather than bend, making repairs difficult and sometimes impossible. For many racing cyclists, however, this is worth the trade-off for ounces; the lighter weight translates directly into better race times.
Which Alloy Is Your Ally?
Choosing a frame material depends on the amount of abuse you expect your bike to undergo, and how crucial a few pounds will be during competition. A steel bike is a perfect choice for an everyday or casual bicycle, since it will perform equally to aluminum for most casual riders. An aluminum racing bike is usually best reserved for a racing cyclist or someone who's training for a race, since it's less expensive than lighter materials like carbon fiber. Ultimately, the fit and design of the frame could have a bigger impact on your ride quality than the alloy itself, so take into account the bicycle as a whole when comparing and contrasting different frame materials.