Dampers

Fast damping

Fast damping is what the tyres feel i.e. reactions over bumps or kerbs. The damper's job is to keep the tyre on the ground over the various surface undulations. Travelling over a bump at speed causes a relatively large and "fast" movement of the damper shaft, and hence it's name.

The rebound setting should always be higher than the bump (1.5 - 3 times on a road car, maybe just 1.33 times higher for a race car). Why? When a wheel hits a bump in the road, the wheel and suspension deflects upwards. We want the energy from that bump to be captured by the spring, so that it transfers as little energy as possible to the chassis. We want the spring to act quickly, so it should be minimally damped when compressing. When the springs rebounds, then is the time to apply damping and dissipate the stored energy.

For fast speed adjustments, pick a bumpy turn at the particular track you're working on. Start with bump at miniumum and rebound at double that value, and work your way up until the front UNDERSTEERS over the bumps, then back off a little. Then do the same for the rear until it OVERSTEERS over bumps, again back off a little. The stiffer the spring the stiffer the rebound setting. Make sure the car likes "usable" kerbs, too. This may require softer settings than done in your bumpy turn test - everything is a compromise.

Slow damping

Slow damping is what the driver feels, i.e. corner entry and exit transitions. The slow damper settings control the dynamic weight transfer and overall motion of the main chassis relative to the track surface as the car is turned, slowed, and accelerated. these motions cause "slow" and small movements of the damper shaft, again the name. The slow rebound usually ends up being higher than the bump, but can be at times 1:1.

Most fiddling will be done with the slow speed settings. First settle on a spring and roll bar setting using a constant radius neutral throttle corner. Next do the "fast" bump adjustments as described previously, then fine tune with slow speed adjustments. First we'll need to understand the different cornering "phases" before we can make a decision as to what slow speed adjustments to make.

Slow damper adjustments

Cornering phase More understeer More oversteer

Entry type 1 Increasing braking + increasing steering

This phase is the first part of a fast decreasing radius turn. This phase will not occur at all if you get all your braking done *before* you turn-in. Since weight is being transferred both forward and outboard, the outside front damper moves in bump and the inside rear damper moves in rebound. these are the dominant two dampers in this phase of turn-in. The other two have minimal effects during this phase.
F bump +
R rebound - F bump -
R rebound +

Entry type 2 Decreasing braking + increasing steering

This is the turn-in phase of a slow corner. This phase may or may not occur depending on the type of turn or driving technique. Weight is being transferred outboard and to the rear, so the outboard rear damper moves in bump and the inside front damper moves in rebound. The other two dampers are considered stationary.
F rebound +
R bump - F rebound -
R bump +

Entry type 3 Increasing steering at constant throttle

This phase can be a chicane turn-in or a turn entry taken at *full* throttle. Weight is being transferred outboard only, so *both* outside dampers are *moving in bump and *both* inside dampers are moving in rebound.
F bump +
F rebound +
or
R bump -
R rebound - F bump -
R rebound -
or
R bump +
R rebound +

Mid-corner transition Decreasing steering back to centre + constant throttle

This is really the opposite of a type 3 entry. It's what happens in the middle of a chicane, as you flick the steering back away from the current cornering direction. As soon as the lateral acceleration passes back through zero, the turn reverts to a type 3 entry again.
F bump -
F rebound -
or
R bump +
R rebound + F bump +
R rebound +
or
R bump -
R rebound -

Exit Decreasing steering back to centre + increasing throttle

This is the apex_to_exit phase. Weight is being transferred inboard and to the rear. The outside front damper moves in rebound and the inside rear moves in bump. The others are considered stationary.
F rebound -
R bump + F rebound +
R bump -

Slow damper adjustments
Cornering phase	More understeer	More oversteer
Entry type 1 Increasing braking + increasing steering This phase is the first part of a fast decreasing radius turn. This phase will not occur at all if you get all your braking done before you turn-in. Since weight is being transferred both forward and outboard, the outside front damper moves in bump and the inside rear damper moves in rebound. these are the dominant two dampers in this phase of turn-in. The other two have minimal effects during this phase.	F bump + R rebound -	F bump - R rebound +
Entry type 2 Decreasing braking + increasing steering This is the turn-in phase of a slow corner. This phase may or may not occur depending on the type of turn or driving technique. Weight is being transferred outboard and to the rear, so the outboard rear damper moves in bump and the inside front damper moves in rebound. The other two dampers are considered stationary.	F rebound + R bump -	F rebound - R bump +
Entry type 3 Increasing steering at constant throttle This phase can be a chicane turn-in or a turn entry taken at full throttle. Weight is being transferred outboard only, so both outside dampers are moving in bump and both* inside dampers are moving in rebound.	F bump + F rebound + or R bump - R rebound -	F bump - R rebound - or R bump + R rebound +
Mid-corner transition Decreasing steering back to centre + constant throttle This is really the opposite of a type 3 entry. It's what happens in the middle of a chicane, as you flick the steering back away from the current cornering direction. As soon as the lateral acceleration passes back through zero, the turn reverts to a type 3 entry again.	F bump - F rebound - or R bump + R rebound +	F bump + R rebound + or R bump - R rebound -
Exit Decreasing steering back to centre + increasing throttle This is the apex_to_exit phase. Weight is being transferred inboard and to the rear. The outside front damper moves in rebound and the inside rear moves in bump. The others are considered stationary.	F rebound - R bump +	F rebound + R bump -

Suggested starting values

Slow bump = critical * 0.7 * (2/3)

Fast bump = critical * 0.7 * (1/3)

Slow rebound = critical * 0.7 * (3/2)

Fast rebound = critical * 0.7 * (3/4)

For example, if the critical damping value is 1,000 ...

Slow bump = 466.6

Fast bump = 233.3

Slow rebound = 1050

Fast rebound = 525

Damper units are Newtons * meters per second