Nearly all kits and many RTRs include extra shock pistons
for suspension tuning. If you look closely at the pistons,
you’ll notice that they have di;erent numbers of holes,
di;erent sizes of holes, or both. ;e smaller or fewer the
holes, the more force will be required to move the piston
through the oil. Generally speaking, smaller or fewer holes
are better for landing big jumps because they will prevent
the vehicle from bottoming out. Conversely, larger or
more piston holes increase handling response and allow the vehicle to soak up small bumps more easily. ;is
assumes, however, that the springs are not too firm or
too soft for the amount of damping the shocks provide—
more on that later.
;e piston with two holes will require more force to move through the
shock oil than the three- or four-hole pistons.
What’s there to understand? It’s a spring! True enough, but what we’re talking about is
spring rate, or “sti;ness.” Spring rate is measured by the amount of weight required to
compress the spring one inch. For example, a “2-pound” spring would compress one inch
if you placed a 2-pound weight on it. A “3-pound” spring would be sti;er since it requires
more weight to compress it the same amount. Some brands state actual spring rates,
other simply label them “soft,” “medium,” and “hard” or something similar. For severe
terrain and big-air action, installing sti;er springs can help your car or truck better cope
with those big hits. Check the accessories section of your model’s manual for optional
;e top coils of these springs
are color coded to indicate
;e higher the number,
the “thicker” the oil.
PRELOAD AND RIDE HEIGHT
Shocks allow you to adjust the amount of static tension or “preload” on the spring. ;is
allows you to compensate for the amount the spring compresses under the car’s weight
and also a;ects the car’s ride height (the height of the chassis over the ground). Depending on the design of your shocks, preload may be set by clipping spacers onto the
shock body above the spring or by threading a collar along the shock body. Less common are collars that clamp around the shock body tightened by a screw, but some models still use them. When experimenting with preload, be certain to set the left- and right-side shocks equally or else your car won’t handle properly (at the very least, it will turn
more tightly in one direction than the other). Clip-on spacers make it easy to set preload
equally—just put the same size and number of spacers on each shock. For threaded and
clamping collars, measure the distance from the shock cap to the collar to make certain
the left- and right-side preload settings are identical.
SHOCK OIL VISCOSITY
;e easiest way to alter damping is by changing the shock
fluid. ;e higher the “weight” number of the shock oil, the
“thicker” it is and the more damping it will provide. Most
cars and trucks arrive with 30-weight oil in the shocks,
and you can typically go as high as 40 weight or as low as
20 weight and still be within the damping range suitable
for your model’s springs. For fine-tuning, you can combine
piston and shock fluid changes. As with all suspension
tuning, experimentation is key. But for play driving, all
that’s essential is that the shocks work!
Clip-on spacers (left), threaded collars (center), and clamping
collars are the three ways preload can be set. Most R TRs use
clip-on spacers, which are goofproof.
PISTONS AND SHOCK OIL
Oil-filled shocks allow damping force to be adjusted in two
ways: by altering the size of the holes in the pistons and
by changing the viscosity (or “thickness”) of the shock oil.
Both methods alter how much force is required to move
the piston through the shock oil. ;e greater the force, the
greater the damping e;ect.