Tom put together this general info on bicycle frame materials and steels available. Aluminum First of all aluminum in general is 1/3 the strength of steel and 1/3 the weight. So to make an aluminum frame as strong as a steel frame you would have to use 3 times the thickness of aluminum... if you use the same diameter tubes as a steel frame. But then you have basically the same weight. To get around this fact and to actually show some weight reduction we use larger diameter tubes to increase the stiffness but since the larger tube is stiffer we can use less material in the wall.  That's how you get a weight savings with aluminum. The downside is that the bigger tubes ride stiffer/harsher/less flexible. The other important property of aluminum is fatigue life. (how many times you can bend it back and forth before it breaks and this is flexing that does not permanently deform it). Steel has a unique property in this department. It is possible to make steel tubing of the right diameter and wall thickness that no matter how many times you flex it, it will never break.  "infinite fatigue life."  Aluminum does not have this property. No matter what you do, there is always a certain number of cycles of bending that will break the tube. Aluminum always has a finite fatigue life. So to make sure an aluminum frame will last a long time you have to over build aluminum a certain amount. Now don't get me wrong. Aluminum is a fine material to make bike frames from. There are a lot of them out there and they last a long time. It is just that if shock absorption/comfort is important then aluminum may not be the ideal material for that bike. Steel Now about the different steels. A couple of general points to keep in mind.
  • All steels weigh the same. A cubic unit of 853 weighs the same as a cubic unit of horse shoe.
  • The stiffness/flexibility of a steel tube is determined by the diameter (cross sectional profile) and the wall thickness. Which steel is used does not matter.
But...
  • if you have several tubes of the same diameter and wall thickness but made from higher and higher strength steels. The higher strength steels can be flexed a greater distance than a lower strength steel before the tube is permanently bent.
In general, the higher the strength of the steel the thinner tubing you can use and still have durability. But the thinner the steel the more flexible the frame becomes. It is a trade off. To compensate, larger diameters and shapes are often used to retain stiffness when using thinner tubing wall thicknesses. Also there is a point in thinning out the wall thickness that denting and crushing become a real problem. When it comes to material selection to build frames things like general stiffness, flexibility, shock absorbency, weight and durability all have to be considered and it is always a compromise between those facts, taking into consideration the use and loads the frame will be put to. Steels available from Columbus(Spirit, Life, Zona), TrueTemper(S-3, OXPlatinum, VerusHT, Verus), & Reynolds(853, 725, 525) 195,000/215,000psi airhardened + special heat treatment to enhance characteristics
  • True Temper S-3
  • Columbus Spirit
  • Reynolds 853Pro (same material as 853 but drawn to the thinnest possible wall thicknesses)
195,000/215,000psi airhardened
  • Columbus Life
  • True Tempe OXplatinum
  • Reynolds 853
150,000-175,000psi
  • True Temper VerusHT
  • Reynolds 725
110,000-120,000psi
  • Tree Temper Verus
  • Columbus Zona
  • Reynolds 525
80,000-90,000psi
  • 4130 - a standard alloy steel used in car and light aircraft frames...and many bicycles
The numbers are the ultimate tensile strengths (point at which breakage occurs). The unit of measure is pounds per square inch (PSI). Note: Columbus (and TrueTemper to a lesser extent) play a lot with shape, diameter and butt length to optimize the functional characteristics of the individual tubes. Note: All the tubing listed above come in a range of diameters, thicknesses and profiles that allow Tom to select the most appropriate tube for your ride. A professional racer has different criteria for ultimate performance than a rider on a loaded tourer has. Tom's 30-plus years of experience is the key here. Let him know how you ride and leave the magic to him!