User Manual

  Input file

    Shim Stack

    Valve Geom

    Aux Components

    Reservoir Pres


  Output file

  Bump Velocity



Reservoir Pressurization System 

Reservoir Pressurization inputs are on the "Plots" or "Res" tab of ReStackor spreadsheets.

  • Bump Height: Max stroke depth and shaft speed for ReStackor calculations of the combined base and mid-valve damping force

  • Oil: Oil viscosity, density and temperature used in calculations

  • ICS, Bladder, Fork: Parameters describing the configuration of reservoir pressurization systems in ReStakcor calculations.

Bump Height:

When you click on the "MV_Analysis" macro button ReStackor runs a set of calculations to determine the combined damping force of the base valve and mid-valve. Those calculations are run up to the shaft velocity specified by Rod Speed and up to the stroke depth specified by L.stroke.

  • L.stroke [=] Bladders, ICS systems and the gas pressure in open chamber forks all depend on stroke depth. ReStackor calculations start with the suspension at full extension and integrate over the stroke up to the stroke depth specified by Lstroke. Lstroke specifies the actual shaft stroke of the shock, not the wheel stroke.

  • Rod Speed [=] Maximum suspension velocity. ReStackor computes the combined compression damping force of base valves (BVc) and mid-valves (MVc) up to the shaft speed specified by Rod Speed. 

Oil Properties:  Oil properties used for all calculations in the spreadsheet.


  • Toil [=] Shock absorber oil temperature in degrees Fahrenheit. Temperature effects on viscosity are evaluated in ReStackor using the Andrade relationship along with companion relationships for the oil density change with temperature.

  • cSt40c [=] Oil kinematic viscosity in centistokes at 40 centigrade [cSt@40C].

  • cSt100c [=] Oil kinematic viscosity in centistokes at 100 centigrade [cSt@100C].

  • Density [=] Oil specific gravity or density in g/cc

  • T.den [=] Reference temperature of oil density spec, usually at 15 or 20 deg C. The specific gravity of suspension fluids range from 0.80 to 0.95 with synthetic fluids at the higher end. 

Reservoir Pressurization Systems 

Gas pressurized bladders and Inner Changer Spring, ICS, systems are used in shocks to pressurize the fluid for suppression of cavitation. Open chamber forks also use the gas pressure buildup as a spring force for bottoming control. The frames below define ReStackor parameters used in each system. 

ReStackor models gas pressurized bladders and ICS systems in forks and shocks.

ICS Configuration

The ICS inputs specify the spring stiffness, float and piston diameter. To run an ICS configuration all of the bladder inputs must be set to zero.

  • Kics [=] Stiffness of ICS spring; [ kg/mm]. 

  • Ncoil [=] Number of coils in the ICS spring. ReStackor uses the number of coils and wire diameter to determine the spring coil bind length and travel of the ICS piston. Push the piston beyond that point and it is going to crack. The fraction of ICS stroke used is reported in the ReStackor output as Nics.

  • Dwire [=] Wire diameter of ICS spring; [mm].

  • FLTics [=] ICS spring float at full suspension extension; [mm]. This parameter specifies the ICS piston motion necessary to engage the ICS spring. Negative values of FLTics preload the spring.

  • Lics [=] ICS chamber length; [mm].

  • Dics [=] ICS piston diameter; [mm].

  • ID.ics [=] Shaft hole diameter in ICS piston; [mm]. For a typical configuration the base valve support shaft passes through the ICS piston. This parameter specifics the shaft diameter and is used to determine the pressurized face area of the ICS piston.

  • Pzero [=] Pzero in the Fork section defines the bleed pressure at full extension of the suspension; [psig]. 

For an open chamber ICS that is vented to the fork gas chamber the values of Pzero, Loil and Ltravel defined in the Fork section determine the gas pressure acting on the ICS piston as the fork is compressed. 

For a closed chamber ICS system the gas pressure above the ICS piston at full extension is set by the Pzero input in the Fork section. This initial pressure increases as the ICS piston compresses gas in the closed ICS chamber defined by L.ics and D.ics, but is unaffected by compression of the fork gas volume. To model a closed chamber ICS the value of Loil and Ltravel in the Fork section must be set to zero. 

Bladder Configuration: Specifies the reservoir bladder configuration used in a fork or shock. To run a bladder configuration all of the Fork and ICS inputs must be zero.

  • P0.blad [=] Initial bladder pressure at full suspension extension; [psig].

  • L.blad [=] Bladder length; [mm].

  • OD.blad [=] Outside diameter of bladder; [mm].

  • ID.blad [=] Normally zero. For a fork, the bladder may have the base valve support shaft running through the bladder. ID.blad is the diameter of the shaft for use in computing the gas volume in the bladder; [mm].

Oil Level Open Chamber Fork

The "Fork" input block defines the initial bleed pressure and oil height with the fork at full extension. To run an open chamber fork all ICS and Bladder inputs must be zero. The value of specifies the initial fork pressure at full extension for both open and closed chamber forks.

  • Pzero [=] Initial bleed pressure of fork at full suspension extension; [psig].

  • Loil [=] Oil height in fork measured from top of fork tube with the fork fully compressed; [in].

  • Ltravel [=] Length of fork travel; [in].