The Midlands Suspension Specialists
 
UK Importers of

 

Technical terms explained.

Aeration:

condition where air bubbles are present in a liquid.

Air-gap:
distance between top of oil in a fork leg, and top of the fork leg.

Air-spring:
suspension using progressive compressibility of air as a springing medium.

Anti-dive:
system used to resist nose-down pitch under braking.

Anti-squat:
extent to which a motorcycle resists tail-down attitude under acceleration.

Bottoming-out:
condition when all suspension travel has been used up.

Castor effect:
self-aligning effect of steering system with positive trail.

Coil bound:
condition where spring coils bear against each other.

Compression (or bump) damping
effect resisting compression of suspension.

Damping:
(usually hydraulic) system for resisting vertical suspension movement.

Droop:
extent to which suspension compresses under weight of stationary vehicle alone.

Fade (go off)
condition where damping effect is reduced by heating of the damping fluid.

Free length:
the 'natural' length of an unloaded spring.

Geometry:
the angles and lengths used in chassis design.

Inertia:
tendency of a moving object to continue moving at the same speed in the same direction.

Momentum:
mass times velocity.

Offset:
in telescopic forks, the distance between the steering head and the fork legs.

Orifice:
passage of precise size through which oil passes as a shock absorber moves.

Oversteer:
condition in which opposite lock has to be applied to keep a vehicle on course through a turn.

Patter/judder:
low frequency vibration emanating from a wheel or suspension.

Pre-load - mechanical:
amount a spring compresses when fitted to a shock absorber.

Pre-load - static:
mechanical pre-load, plus additional compression due to weight of vehicle.

Progressive rate:
one-piece spring which compresses less readily as more loading is applied.

Pro-squat
extent to which a motorcycle resists tail-up attitude under acceleration.

Pumping down:
condition where the ride height of a vehicle lowers progressively over a series of bumps.

Pumping up:
where ride height rises over a series of bumps.

Rake (head angle):
angle between the steering head and the vertical.

Rebound damping:
damping effect resisting extension of suspension.

Rising-rate:
suspension in which the wheel rate rises as the suspension compresses.

Sag:
extent to which suspension compresses under weight of stationary vehicle and rider.

Self-aligning torque:
self-centering steering force caused by positive trail.

Spring rate:
amount of force needed to compress a spring a given distance.

Stiction:
'static friction': the reluctance of mechanically loaded parts to move against each other, esp. in forks.

Tank-slapper:
violent lock-to-lock oscillation of the handlebars.

Topping-out:
condition where suspension is fully extended.

Trail:
distance between the front contact patch & the imaginary point where the steering head centerline would intersect the ground.

Understeer:
condition in which extra steering effort is required to keep a vehicle on course through a turn.

Unsprung mass:
weight of wheels, tyres, brakes (proportion of) suspension, etc.

Wallow:
oscillating, yawing movement of a motorcycle, esp. through a turn - like 'rowing' the bike.

Weave:
(often rhythmic) straight-line instability.

Weight transfer:
amount by which a wheel is loaded & unloaded under braking or acceleration.

Wheelbase:
distance between front and rear axles.

Wheel rate:
force needed to deflect a wheel vertically by a given distance.

 


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