Categories of Mountain Bikes
Fully Rigid
Trek 4000 - circa 1998 - with rigid frame
These are the original mountain bikes. They have no suspension, so you feel every bump, but you also have the greatest pedaling efficiency because none of your energy is being lost in a suspension system. These are generally the least expensive and lightest bikes because they don't have the complexity and weight of a suspension system.
Hard Tail
These bikes have a shock built into the front fork and a rigid rear tire. This is a good compromise because it helps you keep your hands on the handlebars during rough sections, but helps you maintain high pedaling efficiency.
Cannondale F5 Hard Tail owned by Ross Downs
Some riders also feel that the hard tail gives them greater control of the bike. These are generally priced in the middle.
Full-suspension mountain Bike - Giant Trance X2
Full Suspension
Also known as Dual Suspension. These provide shocks on both your front and rear tires. The suspension system allows for a much smoother ride and better traction on the trail. The added comfort and traction usually outweigh the loss of pedaling energy to the suspension and that's why full suspension bikes are the most popular among enthusiasts. On average these bikes are heavier and more expensive. Recent developments in suspension technology have also increased pedaling efficiency so not much energy is lost to "pedal bob".
Trek STP Soft Tail Mountain Bike
Soft Tail
There aren't very many of soft tail bikes. These bikes are defined by a unique rear-suspension design with a small amount of travel in the rear caused by flexing of the frame through the chainstays and a shock in the seatstays. The limited amount of travel (only about 1") has caused these frames to lose popularity even though their simple design causes them to be lighter than other rear-suspension bikes.
Single-speed
There is no shifting involved in a single-speed set-up. Riders ride with one gear in the front and one in the back. The gear-ratio is determined by the strength, skill and preference of the rider. The advantage of a single-speed bike is that it is lighter and less-complicated. In theory, the lighter bike would allow the rider to go faster, and since the bike has fewer gears, then there are fewer parts that could cause a breakdown. Also, the purchase and repair of these bikes are both less expensive.
The disadvantage is that the top-speed of the bicycle is generally lower than that of a multi-gear bike. Also, these bikes have a smaller range of speeds where they can be pedaled efficiently.
29er
These bikes have 29" tires instead of the 26" tires that are found on most mountain bikes. Larger tires can roll over obstacles faster, while the smaller tires are stronger and more maneuverable. 29ers are increasing in popularity.
