SUSPENSION: Suspension Forks

A suspension fork softens the blow of a bump on the road or trail. The fork must be checked for wear and lubricated regularly. The oil and springs should be changed either when they wear or to alter the characteristics of the fork.

How Suspension Forks Work

The suspension fork on the front wheel absorbs the energy of a bump and prevents the force from reaching the rider. The fork’s main spring, which can be trapped air or a metal coil, is compressed as the sliders move up the stanchions. Compression ends when the spring has absorbed the shock of the bump. At this point, the spring pushes the sliders back and the fork rebounds. Damping controls the speed of compression and rebound, usually by absorbing some of the energy of the bump with an air or oil damping mechanism. This creates friction, which slows down the fork’s movements.

Handling bumps: Damping should prevent the fork from reaching the limits of its travel (aka "bottoming out"), but the fork should still be reactive enough to cope with every bump.

Front Fork Compression

Bunny-hopping gives a graphic demonstration of compression and rebound. As the rider picks up the front of the bike to clear the log, the fork rebounds because the rider’s weight has been taken off the spring. On landing, the fork compresses as the spring absorbs the shock of the bike and rider landing.

(left) Pulling the handlebar upward and moving the body backward lifts the front wheel so the front fork rebounds.

(right) Landing on the ground returns the rider’s weight to the bikes frame and compresses the front fork.

How air/oil forks work

When a bump pushes up the sliders on this fork, a piston moves up the left stanchion, compressing the air. Once the bump has been absorbed, the air pushes the piston back and the fork rebounds. The damping mechanism in the right stanchion, which is full of oil, also moves up and down with the bump, controlling the speed of compression and rebound.

• Fork crown: Turns the fork
• Brake arch: Connects the two sliders
• Seal: Keeps dirt out of fork’s interior
• Right stanchion: Contains the damping mechanism
• Oil chamber: Contains oil
• Damping mechanism: Moves up and down with slider
• Slider: Moves up and down on the stanchion
• Left stanchion: Contains the spring mechanism and piston
• Air chamber: Contains air
• Piston: Moves up and down in response to bumps