Penske Racing Shocks 8760 Series - Manual (Page 17)

17
A Guide To Damper Tuning
The following setup procedures are basic recommendations for reaching an initial starting point using double
adjustable Penske Racing Shocks. This procedure is ideal for use on an open test schedule. A race weekend
may not allow enough time. Start by making the compression adjustments as described below, until it feels right,
then move to the rebound adjustments.
COMPRESSION
The idea is to set the compression damping forces to suit the bumps in critical areas, such as corners, corner
exits and braking zones.
Increasing or lowering cannister pressure (range 150 to 300 psi) can have an influence on support under brak-
ing, acceleration, and tire loading on turn in, and on mid-corner grip.
Step 1 - Set the rebound adjuster at full soft.
Step 2 - Starting with the compression setting at full soft, drive a lap then return to increase the
bump settings. Continue this process of adding bump control to minimize the upsets until
the car becomes harsh, loses tire compliance and traction. At this point you know that you
have gone too far on the compression settings; back off one click.
REBOUND
The idea is to tighten up the car, stabilize the platform and eliminate the floating "Cadillac feeling". This will also
reduce the rate of body roll.
Step 1 - With the rebound setting at full soft, add 5 flats (8100) or clicks (8760) of rebound adjustment at a
time, then return to continue the process until the car becomes "skittish" or the rear wheels hop
under braking. At this point you know you have gone too far on the rebound settings, back off
one flat at a time for final balance.
Once again, this is a basic procedure for finding your initial setup for a given track. If you find that you are at the
end of your adjustment range and feel that the car is feeling better, you will need to revalve the shocks to allow
for further adjustment in the given direction.
Basic Start-up Procedure
The range of adjustments will have a relation to high or low shaft velocity depending on what main piston is
being used:
1) Linear Piston 1° - adjustment through range
2) Linear Piston 2° - greater change in low speed adjustment
3) Velocity Dependent Piston - adjustment through range with greater change in low speed
4) Digressive Piston - range primarily in low speed
Also depending on valving, there will be an affect on adjustment range. The softer the valving (A - B), the less
force range it will have. This is due to a lower pressure required to blow the valves on the main piston. Obvi-
ously the heavier the valving (C - E), the more effective the bleed becomes. On digressive pistons, pre-load
also affects the range of adjustment.
Rebound adjustments are usually indicated by the driver asking for more stability. By increasing low speed
damping, stability will be enhanced; decreasing damping will allow more movement in the car, but will result in a
little better tire wear.
Also, the amount of rebound can have a great influence on weight transfer. Less front rebound allows weight
transfer to the rear under acceleration. Less rebound in the rear allows for a greater amount of weight transfer to
the front under braking and turn in.
When a car is over damped in rebound it can pack down in a series of bumps and a driver will recognize this as
too stiff and usually will think it is compression damping. Too much rebound can cause lack of grip on cornering.
When making a large spring change keep in mind where the rebound adjuster is and do you have enough range
to compensate. Sometimes a spring change will bring a better balance to the damping values after the spring
change. If the spring/shock combination was balanced, the rule of thumb is a stiffer spring requires lower
compression and higher rebound. A softer spring requires higher compression and lower rebound.