Damper Tuning Basics

 Damper Tuning Theory 101

While it seems like a black art and sometimes probably is because of other chassis interactions, damper tuning is more scientific than that. Damper Dyno tracing to get the proper damping curves is the ideal way to get it right. Basically one is trying to attenuate the resonant or natural frequency  of the spring/car weight interaction and this is different for each corner. NF or natural frequency is expressed in Hz. Street cars should be 0.8 Hz, Full -race at 2.5 Hz and sports cars or modified cars somewhere in between. 

 

The aim is to arrive at or near "Critical Damping Point". This is when the suspension reaches its rest position after half a cycle i.e once the bump is cleared and the springs are pushing back down, it comes to rest without overshooting. This requires quite a lot of rebound damping to achieve. In normal street going cars damping is more like half-critical or less where the car suspension is allowed to complete one cycle, i.e. one stroke down and beyond and one stroke back. This looks like the car body bounces up then down then returns to resting. Many have less damping than that and the body might only stop bouncing after two cycles.

 

We are trying to get the suspension or body to only move half a full cycle. Without any damping, the spring and body will oscillate for quite a while before returning to rest. However without proper equipment and a suspension dyno it is going to be hard to get the exact point. But not all is lost if we don't have the equipment.

 

Here is where overdamping "helps" us. Not that it is useful on a day to day basis but because too much bump makes the shock stiff like additional spring rate or in the case of rebound it "binds" the spring in a compressed state increasing effective spring rate and in both cases ride quality quickly gets jiggly and skipping occurs. Of course the steering and chassis response seems sharper but the ride is unbearable unless on a track where the road surface is smooth.

For our purposes when we crank in too much damping and the ride gets too jiggly we know that we have past the critical damping point. So dialing it back a bit till it gets more comfortable without the jiggling is close to the critical damping point. Can we get the exact settings with this method? The answer is no but under the circumstances without measuring equipment this gets us somewhere in the ball park.

Of course more damping makes the car feel planted but may not always result in the fastest lap times. For that to happen professional tuners have quoted 2/3 of Critical Point being the best but thats another story altogether, past the scope of this report.

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