Your mountain bike goes up and down, sure. And you know there are a range of adjustments to make it feel and act differently. But have you ever wondered exactly what all those parts are. Here we’ve developed an anatomy guide to your front fork. Depending on the manufacturer, some of the parts might go by a different name.
The steerer tube is a carbon or aluminum tube that slides into the headset and frame of the bike. This is the connection point between the frame and fork, and its length is cut by a mechanic to match rider or manufacturer preference. Contemporary steerer tubes feature a tapered shape, with a wider bottom for added stiffness and strength.
The crown is a metal or carbon piece that sits on the top of the stanchion tubes and below the headtube of the bike frame. Both the stanchion and steerer tubes are pressed into the crown, so it is designed and manufactured to precision tolerances.
The stanchions are aluminum tubes with a smooth finish, which reduce friction on the fork. These two tubes travel up and down as the front wheel engages different terrain. The stanchions also house the air spring (usually in the left tube) and the damper (usually in the right tube).
The lower casting is a one-piece magnesium or carbon tube set that houses each stanchion as it moves through the travel. Also known as a slider or lower, this part also provides mounts for disc brake calipers and thru-axles.
The dust seal is a thin wiper mounted at the top of each lower. As the stanchion moves into the lower, the dust seal wipes away dirt, water, and mud to prevent it from entering the internal systems.
The axle is the connection point between the wheel and fork. It mounts through two perpendicular holes, one on either side of the lowers. Axles are usually threaded on one side to bolt onto the fork and hold the wheel securely.
The damper is an internal system that controls suspension performance. The damper includes suspension fluid, metal shims, a piston, and an internal floating piston (IFP). Together, these components regulate compression and rebound forces by using adjustments to open and close ports that allow the fluid to move through the system.
The air spring is comprised of a positive and negative chamber. The positive chamber holds the most pressure and works in tandem with compressions settings to regulate how firm or soft the fork rides. The negative chamber works against the positive to provide a balanced feel and resist “topping out” or allowing the fork to clunk at the top of the rebound.
The blue knob on the top of the fork - compression adjustments restrict how freely the fluid moves through the damper via ports and shims. The more restriction, the more firm your shock will feel. Depending on the manufacturer, compressions adjustments will have a fully open or soft setting and on the opposite side of the spectrum, a firm or even locked out setting, plus additional settings in between the two for fine tuning to personal preference.
Air Pressure or Coil
Air pressure or metal coils work in tandem with the compression settings and are the main dictator of how the shock will ride in terms of sage, softness, and firmness. A coil is non-adjustable but can we swapped for different stiffness. Air pressure, depending on the style and manufacturer, can be adjusted at the top or bottom or both of the fork.
Rebound works in the same way of compression, but with the opposite effect. After a shock is compressed it will rebound toward its starting position. The rebound adjustment uses ports and shims to restrict the flow of oil in the damper to slow or speed up the rate of rebound.