Penske 8900 series, Technical Manual

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19
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 de-
scribed 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 cor-
ners, corner exits and braking zones.
Increasing or lowering cannister pressure (range 150 to 300 psi) can have an influence on support
under braking, 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, ride a lap then return to increase the
bump settings. Continue this process of adding bump control to minimize the upsets until
the bike 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 bike, stabilize the platform and eliminate the floating "Cadillac feeling".
This will also reduce the rate of weight transfer.
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 bike becomes "skittish" or
the rear wheel hops 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 bike is feeling better, you will need to
revalve the shocks to allow for further adjustment in the given direction.
Basic Start-up Procedure
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 motorcycle 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 com-
pression and lower rebound.