All About Frame Materials
Although over the years there have been such oddities as bamboo (still available!) and plastic frames, current road bikes are made of one or more blends of these four materials: steel, aluminum, titanium and carbon fiber. We get into the differences below.
But first, realize that fine bicycles are built of all these materials. Also, two frames can be constructed of the same material yet have entirely different ride qualities due to differences in geometry, assembly, tube shapes, and material manipulation (reinforcing a tube, for example). Which is one of the reasons it’s so important to test ride and feel the bikes you’re thinking of buying.
A tip for inspecting frames: Look for a tubing decal on the seat tube or down tube. Sometimes manufacturers provide these and they usually help explain what brand and type of material is used in the frame. We’re happy to elaborate if you have questions. Just ask.
Carbon fiber (also called “carbon,” “composite” and “graphite”) is unique because it’s not a metal. It starts out as a fabric that’s impregnated with a glue called resin. The resulting material can be turning into tubes or shaped in molds and is usually cured with pressure and heat turning the material into a solid structure. Frames made of carbon are extremely light, stiff and durable.
Carbon’s greatest advantage is that it can be manipulated essentially in endless ways (because builders can orient the fabric strands however they want), which means it can be fine-tuned to provide just about any ride qualities desired, so it’s possible to achieve supreme lightness with outstanding rigidity and top-notch compliance for comfort, too. What’s more, carbon is impervious to corrosion and can be built into beautiful shapes producing Ferrari-like looks.
Like titanium, because construction is somewhat complicated, and because carbon fabric and resins are in high demand by other industries, carbon frames can be on the high end of the cost spectrum. To describe these frames manufacturers use terms such as “high modulus” and “void free,” which tells you that it’s high-quality carbon fiber material and stellar construction. Sometimes, these designations appear on frame “tubing” decals. Be sure to ask if you have questions about the carbon material used in a frame because there are some amazing designs and we enjoy showing them off.
Carbon is a popular material for forks due to its natural ability to absorb shock while offering fine handling. There are even all-carbon forks (weighing less than a pound). These are great if you want a super-light road bike. (There are other carbon forks that use steel or aluminum for the steerer.)
The most traditional frame material, steel, has been used by framebuilders for over a century. Many types of steel tubing are available and the material is easy to bend and shape. Plus, there are myriad methods of assembly making steel very adaptable to cyclists’ needs. It also offers excellent ride quality, durability, is easily repaired and affordable. If there’s a knock on steel, it’s that it tends to be heavy when low-quality tubing is used (found on bikes sold at department stores). And, while there are new steels almost impervious to corrosion, most types can rust if treated carelessly (protect that paint job!).
Entry-level steel-frame bikes are usually less sophisticated than those typically favored by discerning cyclists and steel fanatics. But, the affordability of the lesser steel frames usually allows you to get a better level of components. And, it’s possible to make a fine-riding steel frame on a budget by cutting back on some of the frills that add cost. For example, such a frame might feature less-costly TIG welding and straight-gauge tubes compared to the fancier lug construction and butted tubes (varying tube wall thicknesses) on the higher-end model.
High-quality steel frames integrate great design, superior assembly, and better alloys in the tubing. A popular quality steel for bicycle frames is American SAE 4130 steel, better known as “chrome molybdenum,” and referred to as “chromoly” or “chrome-moly.” And, there are plenty of other impressive alloys offered by tubing suppliers such as Columbus, Reynolds, Tange and True Temper. Frames built of these materials are famous for their combination of responsiveness and comfort.
Steel is an excellent fork material. It can be formed into any shape; even aero ones. It’s plenty strong. And, it also absorbs shock to soften rough roads. Steel forks are heavier than those built of lighter materials such as aluminum and carbon fiber.
Aluminum was first used in frame construction in 1895. But, it didn’t come into wide use until the 1980s when large-diameter tubing was conceived and construction processes were perfected. Now, it’s the most popular of frame materials. It’s subject to the same variances in assembly and quality as steel. And, like steel, as you spend more, you get higher quality tubing and better construction.
You may hear that aluminum has a more jarring ride than the other frame materials. But, while this used to be the case in its early years, it’s not a problem today thanks to new aluminum alloys, tubing enhancements and improved construction techniques. These allow the frames to absorb shock better than ever while still offering the wonderfully lively ride that makes aluminum all the rage today.
This magic ride is attributed to aluminum being the lightest frame material — even lighter than carbon and titanium. It makes aluminum frames great choices for racing and time trialing. And, unlike most steels, aluminum won’t rust; another advantage.
There are various types of aluminum tubing in use by manufacturers. Some common types are 6061 and 7005, numbers that refer to the alloys in the aluminum such as magnesium, silicon and zinc (pure aluminum isn’t strong enough for bike use). And, there are some super-light tubesets such as Easton’s Scandium. Be sure to ask if you have questions about an aluminum bike in our store and we can explain further.
Aluminum forks are generally stiff and light, and can be shaped aerodynamically. They also offer good vibration damping to smooth the ride.
Titanium (also called “ti”) is one of the longest lasting, strongest, and most expensive frame materials. Some cyclists and experts feel that it combines the best characteristics of all the other frame materials. It rivals aluminum in weight, is as comfortable as steel and it has a sprightly ride and electric handling that many riders swear by. The frames feel “alive,” as if each pedal stroke gets a boost from an inherent springiness in the frame.
Titanium is hard on metalworking tools, requires expensive titanium welding rod and must be joined carefully in a controlled environment. Consequently, titanium frames are very expensive to produce, which explains their high purchase price.
The two common types of titanium are 3Al/2.5V and 6Al/4V. These designations refer to the amount of aluminum (Al) and vanadium (V) alloys used in the titanium. 6Al/4V is more expensive, lighter, harder to machine and stronger. But both titanium alloys are excellent; they may even be combined in a frame.
Titanium forks are rare and very expensive due to the additional costs in material and construction. Also, because extra strength is needed in the fork steerer (the upper tube), ti forks usually outweigh other high-tech tillers. These two considerations are why vurtually all ti frames come with carbon forks.