Physics of ReStackor Shock Absorber
the past, experience and intuition were the only guides in tuning suspensions.
Successful seat-of-the-pants tuning
required a huge experience base to guess the series of shim stack changes needed to correct
a specific suspension problem.
Changing the low-speed stack effects the mid-speed, changes to the high speed effect everything.
Trying to experiment your way into a fix was
more likely to screw up the suspension then fix it.
After tuning one suspension the experience gained would often
provide little help in tuning the next due to difference
in shock absorber valve geometries creating a whole new series of suspension
uses fundamental physics and computer software to create a suspension tuning tool capable of describing the
damping performance of your suspension.
ReStackor references shim stack changes in terms of clicker settings letting you use your real world riding
experience to tune the stack in terms of forces you can actually feel when you ride.
Tuning in software allows you to test hundreds of stack configurations and experiment with shim stack changes
across the entire range of suspension speeds to determine the effect of each feature
of the shim stack on damping performance and tune that feature to produce
the damping profile and suspension characteristics you want.
ReStackor and ReStackor pro use a detailed FEA force balance to
determine the shim stack
stiffness, edge lift and valve face flow area. This
allows you to tune all features of the shim stack including shim
diameter, shim thickness, stack taper, stack float, stack preload,
crossover shims and the stack clamp diameter.
The stack flow area plots produced by Shim ReStackor are reference
bleed circuit "clicker"
flow area allowing you to instantly recognize the effect of shim
stack changes in terms of two clicks stiffer or three clicks softer
and tune the suspension in terms of forces you can actually feel
dynamic flow losses
ReStackor pro uses the fundamentals of fluid dynamics to compute
flow losses and flow resistance through the fluid circuits of
a shock. This allows damping
forces to be computed as a function
of suspension speed and bump height.
ReStackor pro gives you the ability to tune valve port geometries
and the shock absorber fluid circuits as well as
evaluate the effect of oil viscosity on the
damping profile of the
: At high suspension
speeds stiff mid-valve shim stacks can cause
cavitation of the rebound chamber. ReStackor
pro computes the combined damping force of base
mid-valves; the suspension velocities where cavitation
initiates; the effectiveness of bladder or ICS systems in controlling
cavitation; and the damping performance of the suspension when driven
beyond the cavitation limits of an ICS
: The fundamentals of a spring-mass-damper
theory provide the relationship of mass, spring rate and damping
on the response and performance of a suspension.
These fundamentals provide the relationships needed to
scale the damping performance of a
stock suspension, and the rider weight it was designed for, to
the spring rate and damping needed for a lighter or heavier
same relationships also provide a method to scale the suspension
setup of your current bike to the setup of a new bike and preserve
the ride, feel and handling you spent years developing on the
suspension of your old