[Jase007]

I know that some here (besides me) run konis on their track and street cars (and trucks). I thought those that did might find this short instruction on setting bump (1st) and then rebound (2nd) on their struts / shocks helpful. Yes, I know that most Koni sports / specials / classics are single adjustable (SA) for rebound only.

From koniracing.com site:

Road Racing Setup
Adjusting bump

Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension as when hitting a bump in the track. It should not be used to control the downward movement of the vehicle when it encounters dips. Also, it should not be used to control roll or bottoming. [edit]this is why you increase T-bar rate[end edit]

Depending on the vehicle, the ideal bump setting can occur at any point within the adjustment range. This setting will be reached when “side-hop” or “walking” in a bumpy turn is minimal and the ride is not uncomfortably harsh. At any point other than this ideal setting, the “side-hopping” condition will be more pronounced and the ride may be too harsh.



STEP 1: Set all four dampers on minimum bump and minimum rebound
settings.

STEP 2: Drive one or two laps to get the feel of the car. NOTE: When
driving the car during the bump adjustment phase, disregard
body lean or roll and concentrate solely on how the car feels
over bumps. Also, try to notice if the car “walks” or “side-hops”
on a rough turn.

STEP 3: Increase bump adjustment clockwise 3 clicks on all four
dampers. Drive the car one or two laps. Repeat Step 3 until
a point is reached where the car starts to feel hard over bumpy
surfaces.

STEP 4: Back off the bump adjustment two clicks. The bump control is
now set. NOTE: The back off point will probably be reached
sooner on one end of the vehicle than the other. If this occurs,
keep increasing the bump on the soft end until it, too, feels
hard. Then back it off 2 clicks. The bump control is now set.




Adjusting rebound
Once you have found what you feel to be the best bump setting on all four wheels, you are now ready to proceed with adjusting the rebound. The rebound damping controls the transitional roll (lean) as when entering a turn. It does not limit the total amount of roll; it does limit how fast this total roll angle is achieved. How much the vehicle actually leans is deter-mined by other things such as spring rate, sway bars, roll center heights, etc. [edit] again here is where t-bars and upgraded sways have to act in concert with dampening[end edit]

It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering power) at that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as “jacking down.” This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered. This repeats with each subsequent bump until the car is actually lowered onto the bump stops. Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer; if it occurs on the rear, the car will oversteer.



STEP 1: With rebound set on full soft and the bump control set from
your testing, drive the car one or two laps, paying attention to
how the car rolls when entering a turn.

STEP 2: Increase rebound damping three sweeps on all four dampers
and drive the car one or two laps. Repeat Step 2 until the car
enters the turns smoothly (no drastic attitude changes) and
without leaning excessively. Any increase in the rebound stiffness beyond this point is unnecessary and may in fact be detrimental.

EXCEPTION: It may be desirable to have a car that assumes an over-steering or understeering attitude when entering a turn.
This preference, of course, will vary from one driver to
another depending on individual driving style.

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Couple things to note without getting WAY into the details (volumes can be written on this):

Stiffer struts / shocks control the rate of bump / rebound. MATCH, MATCH, MATCH the dampers and spring rates (t-bars).

If you upgrade struts and shocks and DON'T upgrade the T-bars you will over dampen the car (OK to a point e.g. adding koni classics to a 356). If you upgrade the T-bars and NOT the struts / shocks you will go "boing-boing-boing" over the bumps b/c the T-bars can't be sufficiently dampened. Suspend the car's weight with T-bars applicable to the task and then dampen them accordingly. Fine tune with sways.

FWIW

Jase