shock 'target drag force' explained
  • Actual seal drag from the dyno Seal Drag test is recorded on the Sh Dyno tab.
    For example (3342):
  • Dynamic drag force is usually higher and fluctuates.
    For example (3342):
    • w50-16 mv pist drag forces may increase with velocity and pressure due to piston design.
      Sample drag force from 1 thru 50ips.
    • 19, 22, 25, 27, 27, 24, 18, 15, 16, 17
    • Also see  Images > Tuning > Shock Tuning WP > sh_mv > pistband_drag.
  DRAG FORCE IN GENERAL
  • It goes without saying that drag force is noticeable at low velocities such as 1-2ips.
  • Drag force is important in providing chassis stability at these lower velocities.  
  • Response calculations provide a way to measure and compare stability at the lower velocities as well providing a way to analyze and control the bikes wheel and chassis through it's entire range. 
  • Response calculations start at race sag.  The rear wheel hits a bump and compresses.  In the process, the chassis jacks a bit due to firm low speed compression force having a r/c ratio of .80 or slightly less at 1ips. 
  • This allows the rear to stay up in the stroke and help prevent packing.
  • The rebound kicks in, and depending on the size and type of impact, it returns the wheel to full extension, and/or eventually returns the chassis to race sag.
  • Chassis stability relies on drag forces as well as low speed compression force to maintain an even keel.
  • New bikes are fresh and tight.  This newness gives the bike stability and a plush feel, assuming the suspension doesn't totally suck from the factory. 
  • When drag forces are reduced, the bike begins to feel loose and sloppy.  That's usually when things start going south.
  • With that thought in mind, drag forces are very important. 
  • Here's a thought .  Why would you want to run a low drag piston band?  You'll end up with a loose feel and the only way to compensate is to increase low speed compression damping.
  • I've heard it said that the most noticeable difference with a low drag piston band is the rebound.   Using response calculations, it's easy to see that the loose rebound feel is actually a lack of chassis stability at race sag due to a reduction in drag force.
  • We can look at drag force as cholesterol.  There is good drag and bad drag.  The key is to understand, measure, and control these forces, not necessarily try to eliminate them. 
  DRAG FORCE AND TARGET NUMBERS
  • The two primary compression target numbers are created from c-zeta and ca-zeta.
    • Drag force is not used when creating primary target numbers.
    • Drag force and a 'gas force fudge number'* are added to c-zeta & ca-zeta target numbers to get co wogas target.    *[sh target gas force explained]
      For example (3342) at 1ips:
      • (cforce + caforce + gas fudge + source drag force at 1ips) = co wogas target
      • 28 + 1 + 4 + 19 = 52
    • Therefore, c force and ca force are not influenced by drag force.
  • If the actual drag force of the shock being tested is higher than the source drag, the dyno test compression numbers will be said amount higher than the target numbers. 
    For example:
    • actual drag = 19.8
    • source drag = 14.8  [a reasonable drag number]
    • The shock's dyno numbers will be 5 lbs higher than target.
  • Riders feels the overall force of the damper, so drag force is a factor when tuning shocks.
  • CURRENT THINKING, if the drag force differs by only 1-5 lbs from target, then just go with it and don't try to compensate by adjusting the c force.  And error on the side of too much drag, not too little.
    For example:
    • If a particular shock's drag force is 6 lbs higher, keep this in mind in the event rider feedback points that direction.
  • If drag forces are excessive, such as 2016-2019 WP shocks, then you should address the core issue.