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Shock Tuning Tips</span>

The configuration of the shim stack will control most of the dampening of the shock. This is the most common way to increase or decrease the overall stiffness of the shock. By changing the quantity, thickness, and arrangement of the shims, the shock can be tuned for different operating characteristics. There is a valve stack on both sides of the piston. One side controls compression dampening and one side controls rebound dampening. The piston also has a low speed by pass orifice (low speed meaning low piston velocity) or in the case of HPG a series of one or more slits.

Rebound dampening will usually be much stiffer than compression dampening. This is because rebound dampening must resist the force of the spring and because piston speeds are much slower during rebound. There is an unlimited amount of valving combinations and many different versions will achieve very similar results.

Under dampening may be the result of the air & oil mixed (a blown floating piston seal).
If the dampening is close, add one or two shims or simply increase or decrease the thickness of the first or second shim to fine tune the overall stiffness.

In general, the rebound dampening does not need to be changed unless the spring rate is changed. If you increase the spring rate, a corresponding increase in valve resistance is recommended.

It is better to use more thin shims than a few thicker shims as the thin shims will provide better, smoother dampening. However, two .006" thick shims do not equal one .012" thick shim as the two thinner shims would deflect more (softer) than the single thick shim.

If you are using a progressive stack, by making the intermediate shim thicker, the shock becomes softer - you would think that a thicker shim would make the shock stiffer yet what happens is that the thicker (small diameter) shims let the large shims deflect further before hitting the next line of shims in the stack, thus making the shock softer. Another alternative is to go to a different diameter intermediate shim. As stated previously, the combinations are endless.

Shock oil - different viscosities are available but typically a light viscosity is recommended. Thicker oils will increase the dampening however it is difficult to say that "x" viscosity will be "a" percent stiffer than "y" viscosity. Synthetic oils are good but expensive. It is better to have cheap new oil in a shock than expensive old oil. Although it's possible for a pro racer (or a shock dyno) to tell the difference it is unlikely the average rider would notice any difference. Stick with one brand and viscosity that way you have a constant for tuning comparisons.

Keep in mind that after changing springs and oil, the only thing that can be done to the shock is:
1) increase compression dampening or
2) decrease compression dampening
3) increase rebound dampening or
4) decrease rebound dampening

After rebuilding and recharging, bench test the shock. Stroke the shock to ensure full travel and smooth action. If the shaft moves in or out erratically this could indicate air is trapped inside.

Remember, none of the above will make a hill of beans difference if everything in your suspension isn't lubed and moving freely. The cheapest insurance for a good ride is a tube of low temp grease and a can of WD-40.

<span style="color:#FF0000">Click on the attached file for a visual description of the above text:
 

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I would only add the following:

"Keep in mind that after changing springs and oil, the only thing that can be done to the shock is:
1) increase compression dampening or
2) decrease compression dampening
3) increase rebound dampening or
4) decrease rebound dampening"
5.) Orifice size in piston

This becomes important in controlling long slow rollers, stutterbumps and slow shaft speed applications.
 
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