Suspension acts to keep your tire connected with rough ground so you can ride faster with more control. Quality shocks won't turn a rough trail into a putting green, but they will provide extra comfort, especially if you ride over rocks, roots, and other obstacles. Shocks use a variety of materials to soak up bumps. Most common are metal coil springs, often combined with rubberlike elastomer bumpers. Some pricier systems sport air springs, which shave weight and are easily adjustable for rider heft.
More expensive shocks add oil damping.
These expert-level setups offer smooth, controlled action as the fork compresses and rebounds. That is, they don't jolt back at you when you hit an obstacle. Rear suspension adds weight, complexity, and maintenance requirements for the sake of speed and comfort. Dozens of design permutations are available, though no clear winner has yet emerged. Fit and Finish A bike that fits is safer and allows you to spend long, comfortable hours in the saddle.