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   Valving Info 003
 
  Shim distortion

 

Flat disc shims produce a nonlinear load-deflection curve when the shims bend without distortion.  Chart 3 shows a graph of a nonlinear curve.


Chart 3

 

The piston design affects shim stack distortion.  These three pistons would apply the force evenly around the edge of the shim, allowing the shim to bend with minimal distortion.


Picture 5

 

Current piston designs have a 4-port design.  These next two pistons are from a Showa 50mm and KYB 46mm shock.


Picture 6

 

Oil pushing on the four opposing corners of the shim stack will distort the shims as shown below.


Picture 7

 

The shim stack looses most of it's nonlinear load-deflection curve when the stack is distorted.  It is hard to calculate the exact loss, but for the most part, we will assume that all 4-port pistons (of similar design) have a similar affect on the shims load-deflection curve.

  • The amount of distortion affects the curve.  (i.e. more distortion = flatter curve, less distortion = steeper curve)

A 4-port piston would distort the shims, producing a more linear load-deflection curve that might look something like the pink line shown below.


Chart 4

 

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  valving info
valving 001
valving 002
valving 003
valving 004
valving 005
 
  complex stacks
complex shim stacks
 
  more valving info
valving 101
valving 102
valving 103
valving 104
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valving 106
valving 107
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valving 109