An Introduction to Bicycle Frame Materials
Here are the basics you should know about the common materials bicycle frames are made from.
Steel has been around for a while. Durable, easy to work with, usually heavy although it can be used for fancy lightweight bikes.
Popular forms include hi-tensile steel, the crappy stuff used for Walmart bikes. 4130 chromoly, strong, usually BMX bikes. Reynolds, Columbus tubing, various thicknesses. The general rule with Reynolds is the higher the number the thinner and lighter the tubing.
Good ride feel, compliant. Can be used for frame and fork. Some swear by the ride feel of steel. "Steel is real."
However, steel rusts! That's the problem. Use Frame Saver or WD-40 to coat inside of frame. (Link to separate article on this.) You'll want to repaint any rust spots (link to my other article on this.)
Bent frame? Can be bent back into shape. Cracked? Just re-weld it. Usually minor damage will progress to major damage, although slowly. Always look for ripples in paint, etc.
Aluminum is very popular these days. Cheap and lightweight, but not as strong as steel.
Stiff, lively ride feel. But you feel all the road vibrations.
Used only for frame, usually use a carbon fork. Perhaps even carbon seatstays.
Sudden, dangerous failures are possible. Can not be repaired. Lightweight aluminum road bikes can turn into a pile of scrap in one small wreck.
Some benefits of steel and aluminum. Stronger than aluminum, but lighter than steel. Good road feel. Last a long time and do not rust.
Common materials are 3 or 6/4v or whatever...
Popular on high-end road bikes these days. Very stiff for efficient ride, and dampens a lot of vibrations. Some say it feels "dead" as far as road feel.
It is strong, but not like steel. Problem is if there is a scratch or something, that can ruin the frame. Can also fail suddenly.
Not usually recommended for mountain bike use.
Made by carbon fiber threads, into sheets, then into mold and covered with resin. You can vastly alter the characteristics of a carbon frame during the manufacturing process based on fiber direction, thickness, etc.
Crazy shapes are possible too.
Not too common, although there are some specialty builders out there using bamboo. They say it's great for bike frames.