what's the advantage of ALUMINIUM frame
Many materials are used in the construction of modern bike frames, and each has its pros and cons. Though their explosion in popularity is relatively recent, aluminum bike frames date back to the late 19th century; the St. Louis Refrigerator and Wooden Gutter Company's Lu-Mi-Num bike is one of the earliest known examples. With most major bike manufacturers now using aluminum or aluminum alloys in many of their products, aluminum bike frames have become a fixture in the cycling world.
Aluminum is the most widely available lightweight bike frame material. Steel, the most common and oldest bike frame material, is approximately three times the weight of aluminum. Though modern steel bikes have adapted to approach the low weight of aluminum bike frames, aluminum frames require no substantial design changes to remain among the lowest-weight bikes available. Due to its naturally low weight, aluminum remains an ideal and affordable choice for racing and mountain bike frames.
Rust and Durability
Unlike standard steel frames, aluminum bike frames are not prone to rust. This resistance to rust makes aluminum very low-maintenance and ideal for mountain biking and touring cyclists, or for any hobby cyclist who regularly rides in wet conditions. Due aluminum's lower strength compared with steel, titanium and carbon fiber, aluminum bike frame tubes often have thicker walls. Though this does not necessarily provide an advantage over other frame types, thicker-than-standard tubes can be used in aluminum bike frames without making them significantly heavier.
Stiffness affects the feel of a ride, providing stability when sprinting and climbing. Varying levels of stiffness are ideal for different types of riders. Partially owing to their thicker tube walls, aluminum bike frames are often stiffer than bike frames made with other materials. This may make for an uncomfortable ride if you are a mountain biker, because aluminum frames have less give than others when biking on bumpy or rocky terrain. This stiffness may provide an advantage to racing and touring cyclists, however, because the low sway of a stiff aluminum frame allows for more stability, and possibly more speed, when sprinting.
Though generally more expensive than comparable steel frames, aluminum frames are still relatively inexpensive. Due to their durability, rust resistance, stability and low weight, aluminum frames can suit the needs of a range of riders. While the benefits of an aluminum frame may not compare with those of some titanium and carbon fiber bikes, frames made with aluminum are substantially less expensive. Well-rounded, lightweight and affordable, aluminum bike frames are ideal for riders at all levels of expertise.