The most common bicycle frame material, aluminum is known for being corrosion resistant, fairly light (though typically not as light as carbon fiber), and having a high strength-to-weight ratio. It’s also reasonably affordable, making it a popular choice for riders and racers on a budget.
“As a bike builder, it is easier to work,” Barcheck explains. “That helps keep costs lower. It’s also typically stiff and responsive, making it good for criterium racing bikes because it accelerates quickly and delivers snappy handling.”
The downside is that stiffness often means a harsher ride quality because it doesn’t absorb road buzz as well as the other frame materials. Translation: It’s not ideal for bikes that are going to be ridden on dirt roads or long-distance touring, where comfort is of prominent importance.
It’s also tricky to repair, and aluminum fatigues more quickly over time. Thus, the best application of aluminum tends to be in entry level road and mountain bikes, which often costs $1,000 to $2,000 less than carbon frames with similar components.
By far the most commonly used frame material for higher-end mountain and road bikes (including virtually every bike being raced at the professional level), carbon fiber is a composite of carbon sheets that are bonded together in a mold using resin. The primary advantage of the material is that at a given stiffness, carbon fiber is significantly lighter than aluminum, steel, or titanium.
This lower density also means carbon frames do a better job of absorbing (rather than transmitting) road vibration, which translates into a more comfortable ride. And carbon fiber can be formed into complex shapes, giving bike makers greater creative design latitude. This is especially useful when trying to maximize the aerodynamic efficiency of a frame.
“With carbon, you can make shapes that just aren’t possible with other frame materials,” Barcheck says, adding that by varying the alignment of the individual fibers, bike makers can engineer different amounts of stiffness in different areas of the bike depending on need. “For example, you can make high stress areas like the bottom bracket stiffer, but allow for more compliance and flex in the seatstays, which improves comfort. And because it’s not a metal, carbon fiber is more corrosion resistant.”
But that creative flexibility comes with a price. Although their cost has come down some in recent years, carbon fiber bikes are typically the most expensive. These frames are also more prone to fracture than metal, and once that happens carbon becomes fragile, and thus unfit to ride.
Another frame material popular with custom bike builders, titanium shares many of the same properties of steel, but has a greater resistance to corrosion and fatigue (it has the highest strength-to-weight ratio of all metals). That means you can build long lasting, lightweight frames. No wonder many titanium frame makers offer lifetime warranties against manufacturing defects.
Titanium is also renowned for its smooth ride quality that’s on par (if not exceeding) carbon fiber, making it an especially popular choice for custom road, touring, and hardtail mountain bikes.
“In my opinion, it’s the best material because it’s so versatile,” Barcheck says. “It can be really light and stiff, but still do a great job of soaking up road vibrations. I also find it to be a little snappier than steel, so it’s a touch more performance oriented. It also doesn’t corrode so there is no paint needed, which helps shave weight.”
The downside is that titanium is a relatively rare (and thus expensive) material that’s labor intensive to work with, meaning these bikes are typically quite pricey.
Once upon a time, steel was the bike-building material of choice. But its mainstream use has waned in recent years, with carbon fiber and aluminum frames now far more prevalent on bike shop floors. The primary reasons for steel’s decline: weight and cost. It’s heavier than both aluminum and carbon fiber, making it less desirable for high-end bikes. And it’s more expensive to mass manufacture than aluminum, hampering its use on lower end models.
But that doesn’t mean there’s not a place for steel in the bike world. Indeed, it remains a popular material for custom builders, who revere it for its ride smoothing characteristics (especially for touring bikes). The reason for this is that steel is easier and less expensive to work with than carbon fiber, and it's also denser and stronger than aluminum. That means you can use thinner walled tubes, and thus design vertical flex into a bike.
Steel is also very durable, highly resistant to fatigue, and unlike carbon fiber and aluminum, can easily be repaired repair. “I love it for road and cyclocross bikes,” Barcheck says. “It just has an awesome, almost springy ride feel that’s really comfortable on long days in the saddle, or when you’re spending a lot of time on bumpy terrain because you can build in a lot of compliance. The downside is that it can rust. So if you live on a coast, you have to take a little extra care so it doesn’t corrode.”