Eye-to-eye length: The distance between the center of the pivot
locations on either end of the shock at full extension
Eye-to-eye
length: The
distance between the center of the pivot locations on either end of the shock
at full extension. This measurement is important when ordering a replacement.
Stroke: The distance that the shock compresses.
Damper: The body of the shock that contains the hydraulic fluid, piston
and valving (same as shock body).
Damper shaft: The rod or tube that drives the internal damping piston.
Coil/over spring: The classic configuration that uses a metal coil spring,
mounted externally over the shock body.
Airspring: A piston that acts against compressed air or gas to support
the rider. Air springs are integrated into the shock body.
Negative spring: A short-travel spring inside the shock body that
opposes the main spring to soften the first part of its stroke.
Compensator chamber (Also “separator piston”): a sealed piston that rides between the shock
fluid and a chamber filled with compressed gas. As the shock shaft is plunged
into the damper, the shock fluid displaces the compensator piston and
compresses the gas in the chamber to compensate for the added volume of the
shaft.
Piggyback chamber: The same function as a compensator chamber, but it is
moved to a remote location to conserve space, or to shorten the shock’s
eye-to-eye length.
Preload collar: A ring, threaded onto the shock body that supports one
end of the coil spring. Turning the ring increases or decreases the starting
spring tension. This adjustment is used to set the ride height (sag) of the
rear suspension.
Progressively wound spring: A spring with its coils spaced closer
together on one end to create less resistance when it is first compressed.
Blow-off valve: Any type of hydraulic valve designed to resist the flow
of fluid until it reaches a predetermined pressure threshold. Usually used to
protect a lockout-equipped damper from high-pressure damage.
Lockout: Any type of external hydraulic valve that prevents the shock
from being compressed.
Free-bleed circuit: A hole or port that allows shock fluid to bypass the
shock’s main damper piston during the compression and rebound cycles.
Low-speed compression clicker: A valve that restricts the free-bleed circuit
during the compression stroke.
Low-speed rebound: Functions the same as the compression clicker as the
shock is extended.
Sag indicator: Typically an O-ring on the shock shaft that gives a
visual indication of how far the shock has been compressed.
Damper piston: A perforated piston attached to the shock shaft that
reciprocates through the fluid inside the shock body. One-way valves on either
side of the piston meter the flow of fluid to create compression and rebound
resistance.
Spring rate: The amount of force that a spring produces when it is compressed
one inch. If you placed a 300-pound spring on a bathroom scale and compressed
it one inch, the scale would read 300 pounds—compressing it two inches would
read 600 pounds.
