Mountain bikes have suspension, or shock absorber, systems much like cars and motorcycles do. There are different types of suspension systems for mountain bikes, and understanding how mountain bike suspension works will help bike buyers decide what type fits their riding style best.
Mountain bikes use suspension systems to keep the tires in contact with the trail as the bike travels over bumps and through ruts. Essentially, the suspension allows the wheels to move up and down without leaving the ground, reducing the jarring effect of rough terrain.
Forks and Front Suspension
Nearly all mountain bikes have front suspension, contained within a “fork.” The fork looks like a two-pronged tuning fork. At the top is the steerer tube, which fits up into the bike frame. A stem attaches the steerer tube to the handlebars.
Below the steerer tube, the fork then splits into two tubes that fit on either side of the front wheel, connected over the top of the wheel by a brace called the “bridge.” The top or “inner” part of the tube slides in and out of the lower or “outer” part of the tube as the bike travels over bumps, providing shock absorption.
The heart of how mountain bike suspension works is within those tubes: the spring and the damper. The “spring” may be a metal coil or, more typically, an air spring. Air springs are adjustable, so the rider can fiddle with the stiffness of the spring action. Critical to the spring’s operation is the damper, which controls the rate of compression and spring-back in the spring. Dampers on most modern mountain bikes are oil-filled—when the spring compresses, it forces the oil through a small orifice, absorbing and dissipating the spring energy and providing a controlled resistance for compression and spring-back or recoil.
Front fork suspensions are easy to switch out, so long as the replacement fork is the right size for the bike.
Not all mountain bikes have rear suspension systems. Those that don’t are called “hardtail” bikes, for obvious reasons. Hardtails are best for beginners and recreational riders. The rear wheel gives a good feel for the terrain on a hardtail bike.
Full suspension mountain bikes have both front and rear suspension. Rear suspension systems may be integrated into the frame of the bike, making them difficult or impossible to switch out, or they could be visible on the outside, attached ahead of the rear wheel triangle. With rear suspension, a shock absorber, either coil or air spring, is integrated with the rear frame pivot system for the rear wheel. The shock itself sits under the rider, but the angle and design of how it relates to the rear wheel frame and pivot system may be unique to the make and model of the bike.
Selecting a fork and deciding whether to choose a hardtail or full-suspension bike is a major decision that will affect future maintenance and the overall riding experience. If you’re not sure, contact your bike retailer to discuss your needs and your options.