“Steel” is an all-encompassing term for any of a multitude of blends of metals that results in a product that is considered ferrous, that is, magnetic. While iron and carbon are the base materials in steel tubing, many formulations blend additional materials. The average department store bike is made from “mild steel” or “1010” (the metallurgical designation for the material). “Chrome-Moly” or “4130” (the metallurgical designation for a type of Chrome-Moly often used in tubing specific to bicycles are common terms for the type of tubing used in many frames from the 1970s to today. They refer to a blend of materials, including carbon, chromium, manganese, molybdenum, phosphorus, silicon, and sulphur. Columbus’ Nivacrom is a patented blend that improved strength over conventional Chrome-Moly by more than 30 percent.
The best-known manufacturers of steel tubing are Columbus, Dedaccaia (pronounced Day-duh-chai), Reynolds, and True Temper. Other producers have included Excel and Tange (pronounced Tahn-gay).
While it is commonly believed that sophisticated alloys are stiffer than 1010, the fact is that all steels share the same density and therefore the same stiffness. What stronger alloys allow a tubing company to do is draw a thinner-walled tube; less material results in a lighter tube. To add stiffness, the tube is drawn to a larger diameter. The increase in material due to the larger diameter results in a tube that is only marginally lighter than its predecessor.
Steel tubing goes through a process of heat treatment in which the tubes are heated to a critical temperature (that depends on the material’s composition) and then carefully cooled in order to increase the tubes’ strength. The more a tube is heated during frame construction, the greater the loss of this heat treatment. This is why many builders prefer to build frames using lower-temperature silver brazing (low-temperature being roughly 700°F as opposed to the 1,600°F reached in brass brazing). Brazing is a process much like soldering; a thin rod is heated until it melts and that melted metal essentially glues the tubes together. Brazing is explained in greater depth later in this chapter.
Silver brazing is harder to perform than brass brazing. Joints are more susceptible to separation if the tubes aren’t properly prepared, but the tubing isn’t heated nearly as much. A more recent innovation in heat treatment is steel that hardens as it cools—gaining strength—following welding or brass brazing. The process overcomes the liability of strength loss due to high heat. Reynolds 853 and True Temper OX-Platinum are examples of this new generation of steels.
Steel gives a frame builder more choices in construction method than any other material. There are three major methods of joining steel tubes: lugged construction, fillet brazing, and TIG welding.
For most of the bicycle’s history, lugged construction has been used. Lugs are essentially fancy versions of the elbow joints used by plumbers. Many builders will cut and shape them into artful designs.
Fillet brazing is an alternative to lugged construction and involves using brass to solder the tubes together. TIG welding is a recent style of construction for steel. The first frames constructed this way were built in the 1980s. More specific information on construction methods comes near the end of this chapter.
As a frame material, steel is experiencing something of a renaissance. Most builders working in steel do so to showcase their artistic skills in shaping lugs. Many one-man boutique builders perform exceptional work.
Double-butted steel tubing is known for its lively ride. Most riders appreciate the way steel offers a balance between road feel, stiffness, and comfort. Double-butted tubing dampens some road vibration while lending a good feel for the road surface below. This quality is what leads many riders to experience the sense that a steel bicycle is an extension of the rider. Because it is impossible to build a steel frame that weighs a single kilogram (2.2 pounds)—as you can with carbon fiber—steel frames are considered a liability on long climbs and during acceleration.
Due to their weight, steel bicycle frames are no longer ridden by top professional cyclists. The last person to ride a steel frame to victory in the Tour de France was Miguel Indurain, whose last win came in 1995.
The majority of steel frames being built today are constructed in one-man frame shops by artisans equally renowned for their fitting skills and artful construction. Generally speaking, most frames will still run on the order of 4 pounds (lbs.), and while that was a reasonable weight in the 1980s, today it is considered heavy by any standard. That is steel’s liability—its weight.
Bottom Line (on a scale of 1-5)
Visual beauty: 5
Road feel: 5
The most plentiful metallic element in the Earth’s crust is aluminum. That should be good news for cyclists, but it’s not. The process of refining aluminum from bauxite ore into aluminum (the most common varieties used in bicycles are designated 6,000 and 7,000 series) is a nasty, environmentally unfriendly business. Worse yet, bicycle tubing must be made from virgin aluminum; no recycled material can be used.
Aluminum has roughly one-third the density of steel, making it a lightweight material to work with. It also has excellent strength. While not as strong as steel, it has more than 80 percent of the strength of steel in most commonly used alloys. Aluminum, however, does not have an endurance limit. (For reasons I can’t explain, the term endurance limit is rather counterintuitive. A material with no endurance limit will break easily rather than last nearly forever.) Designing an aluminum frame that will last for more than a few years requires a bit of effort.
Aluminum bicycle frames have been made by bonding tubes to lugs and by TIG welding tubes together. Racing frames made from aluminum were introduced in the 1970s. Early aluminum frames were constructed from aluminum tubes bonded to aluminum lugs with an industrial-grade epoxy. The two most popular manufacturers of this frame style were Alan and Guerciotti. The tubes used diameters and wall thicknesses similar to steel frames, resulting in unusually flexible frames frequently referred to as noodles. They remained popular with diminutive women for many years, as no other bikes were available on the market that offered as comfortable a ride in small sizes.
In the 1980s, Klein and Cannondale pioneered large-diameter, thin-walled aluminum tubing. Unlike their predecessors, these frames were TIG welded (the specifics of construction are covered later in this chapter). The frames had a reputation for being lightweight and stiff. Advances in alloys and heat-treating have helped Cannondale continue to reduce the weight of its frames and balance the efficiency offered by increased stiffness with a rider’s need for a modicum of comfort.
Because aluminum frames are susceptible to cracking, precautions must be taken to avoid stresses accumulating in any one part of the frame. Joints where the tubes have been welded together are prone to cracking if there isn’t a smooth transition from one tube to another. Vibrations stop anywhere there isn’t a smooth transition. Such a location where stresses can collect is called a “stress riser,” and it’s considered a time bomb in an aluminum frame. In order to cut down on the possibility that the stress riser will encourage a crack to form, the extra material added in welding, called the “bead” of the weld, is typically smoothed by a small, hand-held grinder called a dynafile.
The Italian bike industry embraced aluminum wholeheartedly in the 1990s. Italian tubing manufacturers began offering lightweight aluminum tube sets to builders as typified today by Columbus’ Starship tubing. This was the beginning of a radical shift in the Italian bike industry, an upheaval that wouldn’t stop for 10 years.
By 1996, aluminum frames had largely supplanted steel as the dominant material for racing frames. There were some pro riders on titanium or carbon fiber frames, but steel had been banished.
Today, aluminum is alloyed with other materials, notably scandium and magnesium, to increase the material’s strength. Increased strength means the tubes can be drawn thinner, thereby decreasing their weight. Some manufacturers use a method called hydroforming, where hydraulic pressure is used to shape each individual tube.
Aluminum is usually known for a very stiff ride. While the bonded frames from Alan and Guerciotti were lauded as comfortable on the roughest roads (Sean Kelly twice won Paris-Roubaix while riding an Alan frame), aluminum’s more recent history has suffered a public relations challenge. The large-diameter tubes used in aluminum bikes for many years gave the bike a stiff, responsive feel that was great in sprinting, but murder on anything that wasn’t glassy smooth. More recently, manufacturers (led by Cannondale) have decreased the harsh ride of the big-tubed bikes, but in general, they are still stiffer than nearly any steel bike. Aluminum tends to be most successful in larger bikes—anything larger than 56 cm or so. For tall riders, aluminum is a sure-fire way to get a stiff frame that won’t weigh 4 lbs.
Aluminum was last ridden to victory at the Tour de France in 1998. Aluminum has suffered the very fate it dealt steel—supplanted by carbon fiber as the dominant material used in top racing machines.
Aluminum is offered in some high-end frames, but for the most part it has become a more budget-oriented material for most manufacturers. For example, Trek’s aluminum bikes are more affordable than its carbon fiber bikes.
Visual beauty: 3
Road feel: 2
Titanium is the marvel of all the metals used for bicycle frames. It is the fourth most plentiful metallic element in Earth’s crust, so there is plenty to make into Russian subs and airplane hydraulic lines, not to mention bicycle frames, but the material is even harder to extract from ore than aluminum. Producing titanium tubing is an expensive process because it is labor intensive and requires large amounts of energy.
Titanium carries half the density of steel and half the stiffness (modulus of elasticity). As a result, it has virtually the same strength-to-weight ratio. What is different is its elongation: how much it can bend before breaking. With roughly double the elongation of steel, on paper titanium looks indestructible. Titanium, like steel, can be built into a stiff or flexible frame, depending on the builder’s (or customer’s) taste, whereas with aluminum, a stiff frame is virtually required to give the frame a respectable life span.
Titanium is most often found in two alloys referred to by their chemical designation: either 3Al/2.5V (94.5 percent titanium/3 percent aluminum/2.5 percent vanadium) or 6Al/4V (90 percent titanium/6 percent aluminum/4 percent vanadium). The first, 3Al/2.5V, is far more common than 6Al/4V, which is mostly seen in frame fittings such as dropouts and cable guides. Both alloys have high yield strength. Titanium is also available in a “commercial pure” (CP) form with no other metals alloyed. This is the type of tubing that the first titanium builders (led by Teledyne) used; it has also been used by other manufacturers, and almost always to poor results. CP tubing has a reputation for cracking under load.
The challenge to building a top-quality bicycle from titanium comes primarily from its elongation. Though it has great density and modulus numbers, mechanically speaking, the metal is difficult to draw into tubes thin enough to take full advantage of its other properties.
The only construction method anyone uses in conjunction with titanium is TIG welding. The first frames made from titanium were produced by an American company called Teledyne. The frame tubes were TIG welded, just as they are today. While a few manufacturers have experimented with bonding titanium tubes into lugs, that construction method has been rare.
TIG welding titanium is unlike welding any other frame material. Titanium is extremely susceptible to contamination by oxygen. When welding titanium, the welder must set up an elaborate argon gas bathing system that prevents oxygen from contaminating a weld as it is made. Due to its incredible elongation, the frame manufacturer must also use special tools when cutting or machining titanium.
Merlin Metalworks, a Boston-based company, was the first company to enjoy commercial success with titanium frames, starting in the mid 1980s. Soon after, the company that is today the largest player in the titanium market, Litespeed, got its start. Eventually, Litespeed’s parent company bought Merlin.
While titanium can be painted just like steel or aluminum, most titanium frames are sold unpainted because natural titanium can have a beautiful luster to it. Surface finish varies broadly from one company to another, though, with some imported frames looking more like a firearm than a bicycle. Because titanium demands careful and precise work, a primary indication of a builder’s care can be found in the consistency of the weld. Merlin has touted its welders’ double-pass weld beads, which look like drops of titanium water lined up shoulder-to-shoulder. Many builders still use this style of weld to this day; great examples can be found on bicycles from Seven Cycles and Moots. This is another reason titanium frames are expensive: the skill required to execute a both beautiful and uncontaminated weld is exceptional and this workmanship is hard to find.
While the boundaries for titanium seem nearly endless, no builder has been successful in maintaining stiffness while managing to shave weight below 2.5 lbs.
While it is true that the first titanium frames were all unusually flexible, today it is possible to purchase a titanium bicycle across a broader spectrum of stiffness than you can from any other material. Titanium’s greatest selling point—aside from its easy-to-clean finish—is the surprisingly resilient feel the material offers. Most riders who have ridden both titanium and steel say titanium has all of steel’s best qualities, and more.
While titanium has been ridden in the Tour de France, it has never enjoyed the widespread success of steel or even aluminum. Today it has been supplanted by carbon fiber at the professional level. Much of this is attributable to a titanium frame’s high cost.
Titanium remains attractive because some builders offer exceptional workmanship with the flexibility of custom sizing and even custom geometry. Seven Cycles has taken this range of possibility to its logical conclusion, offering a rider custom sizing, custom geometry, and custom tubing, so that the bike will feature exactly the stiffness the rider wants. And while there are relatively affordable titanium bikes on the market, that silvery luster remains a status statement.
Visual beauty: 4–5
Road feel: 5