Penske Racing Shocks 8900 Series - Manual (Page 9)

The damping characteristics of your shock are determined by the compression
and rebound valve stacks located on the main piston.
The valve stacks are made up of a series of high quality shims, which are made
to flex under the force of oil flowing through the piston ports and then return to
their original state.
The thickness of the individual shims determines the amount of damping force
the shock will produce. By changing the thickness of the individual shims,
damping forces will be altered. For example, if you are running an “A”
compression valving, where all the shims in the stack are .006 thick and you
replace them with a “B” compression valving, which consists of all .008 thick
shims, the compression damping will increase.
* When the shaft is moving very slowly oil passes through the bleed hole, if
there is one, before it passes to the shims.
Guide to Damper Tuning
The ultimate purpose of a shock is to work together with the spring to keep the
tire on the track. In compression (bump) to help control the movement of the
wheel and in rebound to help absorb the stored energy of the compressed
spring.
Usually in rain or low grip situations allowing more bleed or less low speed
damping is desirable to delay tire loading upon initial roll.
In dry high grip conditions adding damping or restricting bleed will load the tire
sooner upon initial roll increasing platform stability.
A motorcycle with too much low speed damping will usually lack grip in change
of directions, cannot put power down in slower corners (wheel spin) and lack
overall grip after initial turn in. If traction is a problem coming off slow corners,
reducing low speed damping or adding more bleed will help weight transfer at
the rear thus increasing traction.
One of the most important things to know about these adjusters is their relative
position to one an-other. If for instance you have the low speed set at 25 to 30
clicks (soft), the range of high speed adjustment will be lessened. Or in the op-
posite direction, if the high speed is set at 0 to 1 (off soft), the low speed adjust-
ment range will be lessened.
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