Damping Rates explained

[KraftwerkTurbo]

Myself and few other Audi Allroad enthusiasts are not satisfied with our stock suspension, as well as the only alternative from a supplier, offering a modified Bilstein (physical, to fit the air suspension; NOT internally) shock.

Most of us upgraded to the stiffer (NO INFORMATION ON SPRING RATE) air bag, but find the shocks underdampened.

One of us has modified an off the shelf Koni shock to fit our air suspension. He has used a Koni shock.

There is NO information available from Bilstein or Koni (or the Audi Allroad stock shocks) regarding usable DATA.

The shocks in question are:

Audi Allroad OEM stock front shock
Bilstein: 24-025935 , BE5-2593
Koni: 82-2488 SPORT
Alternative Koni: 82-2516 Sport

Someone dug up this information (shown as it was given to me) for the Koni:
82-2516 Sport between 3900-520 m/c
82-2488 Sport between 1800-520 m/c

A) I read that damping is measured in Force (Newtons) at a given speed (0.52 m/s)?
B) Does anybody have the damping values for the Audi Allroad stock front shock and above Bilstein and Koni shocks?
C) Interpreting above numbers, could it be 3900N/1800N?

The Koni 2488Sport is said to be firmer than the OEM shock, and firmer than the Bilstein. The 2516Sport may be TOO much.

Can some of you experts shed some light on us 'suspension newbies'?
Hard data for the shocks in question?

 

[cibachrome]

Well, to start it off, NO 'shock' has just a pure linear rate for jounce and rebound, so single numbers are meaningless. The test procedure and even the machine used to produce useful data is usually specific to the vehicle certainly the manufacturer of the vehicle AND the damper. In each velocity direction, there are usually 2 rates for force vs. velocity: a low speed rate, a high speed rate and a velocity where the rates change. The jounce and rebound rate sets are usually NEVER the same. There is hysteresis, too. And that involves whether the damper is tested with its mounts or without all the vehicle mounting hardware.

Lastly, there is the internal hardware set: blowoff valves or springs and discs and of course gas pressurization (or not). Damper testing is usually not for amateurs because of the fluid and facility contamination problems. And you need so-called "Take-Apart" dampers and a kit with many different part characteristics so you can run experiments and evaluate your constructions or 'recipes'. Then you need to try to construct the working damper set from the test press values.

There are dampers made for racing that would fit the requirements for reuning your vehicle. But you will need the kits, operator, evaluator and test machinery to do a good job. Teams and builders I have worked with will build a dozen units with the same recipe in order to make sure that the one specific part going on the vehicle is working according to the build recipe. That's because of errors, dirt, water in the fluid, fatigued springs and an evaluator having a bad day.

Your air springs add another layer of complexity because of THEIR contribution to the system function (plumbing, semi-active, flow control, less friction, etc.).

If you want to try new technology, get a set of the Cadillac rheological shocks (electro fluid property alteration) units and get them to adjust on the fly to emulate a passive damper. Then have it tested and build a passive set from the test press results. This is kind of fun to do. But, it takes an extra layer of knowledge and skill to fire the Cadillac dampers in a passive emulation. Then go find your favorite bumps (and all identical bumps are not the same). Go figure.