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Damping - The process of
absorbing the energy of impacts transmitted through the forks or rear
shock on the compression stroke, and the process of absorbing the energy
of the spring on the rebound stroke.
Damping Circuits - There are normally four damping
circuits which affect the damper's speed. There is both a low and high
speed circuit for the compression and rebound strokes.
Damper - A fluid chamber
with a means of regulating the fluid flow to restrain the speed of the
moving end of the damper during the compression or rebound strokes. A set
of forks and a rear shock are considered dampers.
Damper Speed - The relative
speed in which the moving end of a damper compresses or
rebounds.
Compression Damping - The damping circuit
that absorbs the energy of compression forces on the damper.
Rebound Damping - The
damping circuit that effects the stored energy release of the compressed
spring in order to reduce the rebounding speed of the
damper.
Falling Rate - The force
required to compress the suspension decreases as you move through the
travel.
Linear Rate - If
the spring rate is linear the suspension will require the same amount of
force to compress it at any part of the travel.
Rising Rate - The
force required to compress the suspension increases as you move through
the travel.
HSC - High Speed Compression
damping is the damping circuit in the shock absorber or suspension fork
that is tuned to provide suspension travel control at high speed over
square edged bumps. Too low of HSC damping will cause excessive bottoming
out in rough terrain. Too high of HSC damping will minimize suspension
travel in rough terrain and cause loss of traction.
LSC - Low Speed Compression
damping is the damping circuit in the shock absorber or suspension fork
that is tuned to provide suspension travel control at low damper speed
conditions. Too low of LSC damping will cause the excessive travel use,
brake dive and wallowing of the bike on small bump terrain. Too high of
LSC damping will cause loss of traction on small bump terrain.
Packing - A term used to describe
the ride characteristics of a rear shock or fork that has too slow of a
rebound setting. A damper with to slow of a rebound setting will stay
compressed after hitting one bump and cannot rebound quickly enough to
absorb the impact of the second or third bump. The solution is to adjust
the rebound to a faster setting.
Preload - Preload is applied to
the fork and shock springs in order to bring the bike to the proper sag
dimension. Adjusting preload to the proper sag dimension insures traction
as wheel load gets light and drops into bumpy holed sections of
terrain.
Sag - This term refers to number of
millimetres that the forks or shock sag with the rider on the bike in full
riding gear. This is essential to proper suspension tuning but is often
overlooked or adjusted incorrectly.
Stiction - A combination of the
words static and friction. This word is used to describe the tension
exerted on the moving damper parts by the stationary parts like the
bushings, seals, and wipers. Low stiction is desirable because it has less
of an effect on the damping.
Top Out - Is what happens when the fork
or shock is fully extended, negative springs and rebound damping prevent
this.
Bottom Out - This
occurs when the suspension has reached maximum travel.
Damper Internals
Shims - A thin, steel,
round, flat washer used to exert resistance on the oil flow through a
piston. A series of shims (valve stack or valving) with varying outer
diameters and thicknesses are arranged in sequence to provide a damping
effect.
Valves - A term that refers
to a series of shims either for the compression or the rebound
damping.
Lock Out - Switches the
suspension off.
Lock Out Blow off Threshold - This is the
force required to move the fork or rear shock when in Compression Lock-Out
mode.
Nitrogen - An inert gas used
to pressurize the Internal Floating Piston (IFP) or Bladder system in a
gas charge shock damper. Note: Air is about 75%
Nitrogen.
Viscosity - A rating
system for oils that measures the oil's flow rate through a fixed orifice
at a certain temperature. Also known as the oil's weight. Example: SAE 7
Wt.
Viscosity Index - The flow rate
characteristic of the oil over a range of temperatures. The VI rating of
an oil is directly linked to the oil's transmissibility. FOX High
Performance Synthetic Suspension Fluid has a very high VI # of 300.Valves
- A term that refers to a series of shims either for the compression or
the rebound damping.
Springs
Spring Rate - Spring rate is described by
force, in pounds or kilograms, needed to compress the spring one inch or
centimetre.
Coil Spring - Consist of a metal wire
formed into a coil that can store energy when compressed and releases
energy as the load is taken off.
Air Spring - Is a contained
column of air inside a compressible container such as a bellow or sleeve.
They can be used as a primary suspension spring or a secondary component
inside a coil.
Spring Curve - A spring
curve is a graph of Force [y-axis] versus Travel [x-axis] measured during
compressing a spring system.
Negative Spring - A negative spring is
oriented in such a way that it tends to compress, rather than extend a
suspension shock or fork. A properly tuned negative spring provides an
opposing force equal to the seal drag which eliminates the feeling of
friction in an air spring system. Negative springs can be a separate air
chamber or a small coil spring, Or a transfer port that allows air to pass
from the positive air chamber to the negative chamber at the beginning of
each movement of the shaft stroke. This transfer port system automatically
balances the pressure for the perfect negative spring for any pressure
setting.
Bicycle
Chassis
Tripple Clamps - Suspension forks that
clamp in three places; duel crowns and a bolt through axel, triple clamps
and can be conventional or upside down.
Swing Arm - The connecting structure
between the main pivot and rear axel.
Rockers - The two plates connected to the
shock and the rear chassis - walking beam and four bar linkage.
Linkage - link plates connected to the
shock and the rear chassis, most often situated around the B/B
area.
Unsprung/Sprung Weight - The unsprung
weight of the bicycle are parts like the wheels, brakes,swingarm and
suspension linkage, and the lower front fork legs. The sprung weight is
all the parts of the bicycle that are supported by the
suspension.
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