The cost of a mountain bike frame is directly based on the material used in its construction, as well as the treatment that the material has received.

Currently, there are five types of material commonly used in the construction of mountain bike frames – high tensile steel, chromoly steel, aluminum, titanium, and carbon fiber

High tensile steel is a durable and inexpensive alloy that’s found in entry level mountain bikes. It comes with a high carbon content which makes it less stiff than chromoly steel, so more material is needed to make it stiff enough for a frame, which will in turn make it that much heavier.

Chromoly steel or more commonly know simply as chromoly, is best described by its major additives – chromium and molybdenum. This is probably the most refined framing material, giving many years of dependable service. Depending on the type of heat treating and butting, you can find this material in bikes of all price ranges. The chromoly steel material offers excellent durability and a compliant ride characteristic.

Aluminum has been refined pretty much in the same way as chromoly. There have been various alloys developed, along with heat treatment and butting. Aluminum is a light material, so frames can be oversized in diameter to increase stiffness without adding much to the overall weight. A dual suspension mountain bike frame is often made with aluminum, since it’s generally the stiffest and most cost effective.

Titanium frames remain expensive because it’s more difficult to weld the tubes to the frame. Titanium is an alloy, normally mixed with small amounts of vanadium and aluminum to give it better weldability and ride characteristics.
More compliant than chromoly, it gives better fatigue and corrosion properties.

Carbon fiber is a synthetic composite material, and is extremely light, strong and stiff. The frame can be custom built to add strength in specific areas, and reduce weight in others. A carbon fiber frame was used initially for the professional level sport rider, due to their initial high cost, but they are now available on more everyday bikes.

The material you choose for your bike, all depends on where you ride, what style you use and what your budget is.

Almost all materials will last you for many years, as long as you take care of your bike and treat the frame with some respect.