Like any other extreme sport mountain biking has its own share of sport specific words. In order to understand some of the phrases and lingo you have to spend some time talking with people who ride mountain bikes or work on them. Since its inception mountain biking, as a sport, has evolved into a creative genre that reflects the uniqueness of bike builders and the riders.
Mountain biking began with bikes that were fully rigid. Fully rigid bikes were bikes that had no suspension whatsoever. Fully rigid bikes have a solid frame, be it steel, titanium, aluminum or some type of other composite metal. A solid frame bike rides much faster than a bike that has a shock absorber (front or rear suspension). However, in the sport of mountain biking rigid bikes do not make for faster bikes as they do in road cycling. Mountain biking demands that bikes be able to absorb the terrain around them. Trails are not always beautifully combed singletrack. Riders have to navigate through ruts, over roots, rocks, and river-beds, over boulders, and down washout trails and water bars. A bike that is fully rigid will bounce like a pinball over many of these obstacles, making it extremely difficult to navigate. Not only does it make it difficult to navigate but it forces the rider to slow down, which is not always a good thing, especially when racing.
Enter the front suspension fork. The front suspension fork looks similar to what you might find on a dirt bike motorcycle. The fork made up of two cylinders on either side of the front tire. The cylinders move in and out of each other as the front tire encounters obstacles, allowing the shock of the hit to be absorbed by the cylinder fork. This allows the rider to maintain maximum speed as well as ride over or on top of objects that would otherwise be avoided.
A bike with a front fork shock absorber and no rear suspension is known as a ‘hardtail’ mountain bike (for a fuller understanding of rear suspension please look up full suspension bikes). Hardtails are what the sport of mountain biking was really founded on. Many would argue that riding a hardtail is experiencing mountain biking in its trues form.