The predecessors to today’s steel frames were first produced in the 50’s. Technology has not changed much since then, and the ride of a steel frame is still the standard by which all other bicycle frames are judged. Steel can be described in general terms as lively, solid, and predictable. Steel's durability and tunability make it a favorite of many cyclists.
The steel tubing used by bicycle frame manufacturers typically falls into one of three basic categories: microalloy; heat treated cromoly; or standard 4130.
Microalloys include Columbus Foco™; Reynolds 853™; True Temper HOX Gold™; and Dedacciai Zero™ tube sets. Microalloys are unique in that they become stronger after welding due to air hardening. This means the tube itself gains strength, and its fatigue life enhanced. In addition, the tube fabricator can make the tube thinner and thus lighter. These are the lightest, yet strongest, steel tubes. Generally speaking, the ultimate strength of microalloys falls into the 170-190ksi range.
Heat-treated cromoly tube sets include Columbus Nemo™; Columbus Genius™; Reynolds 725™; True Temper OX 3™; and Dedacciai Zero Tre™. These tubesets are characterized by: high strength and good workability (formability); a wider variety of tube set options; and the ability to be brazed without damaging the tubes. Their ultimate strength typically falls between 150-175ksi.
Standard 4130 representatives are Columbus Brain™; Reynolds 525™; and True Temper OX 2™, among others. This material has good formability, and is used to create thicker, more stout tubes. Thus, optimally, these tubes would be used when building a frame for a larger rider. Ultimate strength generally is in the 120-150ksi range.