Q: Why are mountain bikes made from carbon fiber? A: Carbon fiber is a material that's built up in sheets over foam forms. Sheets of carbon-fiber cloth are placed over the foam forms and epoxied in place. The result is ideal for a bike frame because it has a very light, strong structure that can have almost any shape.

If you've been on a biking trail in the last few years, you've probably seen all kinds of crazy-looking bikes. If you've read "How Bicycles Work," you already know the basics, so in this article we'll take a look at some of the new stuff on today's mountain bikes, including:

• More gears (Some bikes have as many as 27!)
• Advances in sprocket technology that make changing gears easier
• Shift levers that automatically go up or down one gear at a time
• Front and rear suspension
• New frame designs and materials
• New brakes, including hydraulic disc brakes
  

If you enjoy mountain biking, then you should check out the adventure sports article, video and images at Discovery’s Fearless Planet to find out what new adventure sports are out there.

Mountain bikes are very popular and boast some pretty
cool technology. See more mountain bike pictures.

In this edition of HowStuffWorks, we'll take a look at all of this new high-tech gear. Let's start with the gears.