26
SHOCK ABSORBERS
1.9
Shock absorbers, or shocks, are the
suspension components that allow the
wheels to keep as much contact as possible
with the track surface. All off-road cars
& truggies have fully-independent front
and rear suspension, meaning that the
suspension at each corner of the car (front
left, front right, rear left, rear right) moves
and may be adjusted independently of the
others. As such, there is a shock absorber
at each corner of the car. Damping,
mounting position, spring tension, and
spring preload are all characteristics that
determine how the shock performs.
SHOCK DAMPING
1.9.1
Shock damping manages the resistance of the shock to movement, as the internal shock
piston moves through the shock oil when the shock compresses and rebounds. Damping
mainly has an effect on how the car behaves on bumps and jumps, and how it reacts
initially to steering, braking, and acceleration.
Damping only comes into play when the suspension is moving (either vertical wheel or
chassis movement or due to chassis roll), and loses its effect when the suspension has
reached a stable position. Without damping, the shock springs would cause the shock to
“pogo” or “bounce” (compressing and rebounding) until it stabilized.
When the shock is compressing or rebounding, the shock oil resists the movement of the
piston through it. The amount of resistance is affected by several factors:
• Viscosity (thickness) of the shock oil
• Restriction of oil fl ow through the piston (affected by the number of holes in the piston
and the hole diameter)
• Velocity (speed) of the piston
Damping is affected by both shock oil and shock piston settings; getting the optimum
shock damping typically requires a lot of “hands on” experience.
EFFECTS OF SHOCK DAMPING
The effects of damping are often diffi cult to distinguish since there is an adjustment
where grip is optimum. When you get away from the optimum damping setting, either
softer or harder, the car will always lose grip.
The table below describes the handling effects by changing damping on one end of the
car; the starting point is always the ideal “optimum.”
ADJUSTING WITH...
EFFECT
SHOCK
OIL
PISTON
HOLES
Front Shocks
Softer
Damping
Thinner
More holes/
Larger holes
• Increases steering on low grip surface
• Slower steering response
• Decreases initial steering at corner entry
• Increases oversteer at corner exit/under
acceleration
Harder
Damping
Thicker
Less holes /
Smaller holes
• Faster steering response
• Decreases steering on low grip
• Increases initial steering at corner entry
• Increases understeer at corner exit/under
acceleration
Rear Shocks
Softer
Damping
Thinner
More holes/
Larger holes
• Increases rear grip at corner exit/under
acceleration
Harder
Damping
Thicker
Less holes /
Smaller holes
• Decreases rear grip at corner exit/under
acceleration
SHOCK PISTONS
Typically, shock pistons are provided with
different sizes of the holes. The sizes or
number of holes affect shock damping by
altering the fl ow of oil through the holes.
• More holes or larger holes give softer
damping
• Fewer holes or smaller holes give harder
damping
