The black art of shock damping ?
The black art of shock damping ?
(OP)
I've enjoyed reading 52 pages of Tips many of which included suspension natural frequency and shock damping calibration, which obviously several people here do for a living. I also "get it" in regards to shocks having the same damping profile/rate but having completely different "feel" because of how the different areas of valving transition.
So the obvious question without giving away any trade secrets is how can one determine what "feel" is possible for a given damping profile? In other words from what little I know about shim stack calibration, it looks like thinner shims in a higher quantity might be preferred over a few thicker shims as the thinner shims might provide a smoother transistion and thus a better perceived ride. I used "might" several times because in all black art there are few absolutes, <LOL>.
Where I'm going with this is when you have a custom shock built for a sports car with performance handling in mind and it's calibrated based on the application and suspension frequency using typical 65% critical damping for low speed damping and a digressive rebound profile, with fixed bump damping, how can you determine:
1. What changes if any will improve the ride or handling from the baseline calibration?
2. Should bump be altered or just rebound to improve ride quality?
3. Is all the above subjective as some folks have very sensitive arses and others do not?
Any and all help appreciated including "speed secrets".
So the obvious question without giving away any trade secrets is how can one determine what "feel" is possible for a given damping profile? In other words from what little I know about shim stack calibration, it looks like thinner shims in a higher quantity might be preferred over a few thicker shims as the thinner shims might provide a smoother transistion and thus a better perceived ride. I used "might" several times because in all black art there are few absolutes, <LOL>.
Where I'm going with this is when you have a custom shock built for a sports car with performance handling in mind and it's calibrated based on the application and suspension frequency using typical 65% critical damping for low speed damping and a digressive rebound profile, with fixed bump damping, how can you determine:
1. What changes if any will improve the ride or handling from the baseline calibration?
2. Should bump be altered or just rebound to improve ride quality?
3. Is all the above subjective as some folks have very sensitive arses and others do not?
Any and all help appreciated including "speed secrets".





RE: The black art of shock damping ?
Your question number 1 is difficult answered for the same reason. If I start with the question "improwed handling" that is the first thing you sort out what action is better. A large part are therefore of the person driving the car must be able to specify what he wants for the properties, which is often not the case. In the case of ordinary cars, there are standardized solutions for shock absorbers, but if you want to run more sporty driving so will the driver's wishes enter the picture. That view is no shops that sell auto parts are particularly interested to disclose, because it will require personal service and is also becoming too expensive. Moreover, it is difficult even for a shock absorber manufacturer to determine the valve setting that gives the customer the right shock absorber.
If we take sub-question 2 so the answer is a little easier. The car has the weight, the wheel weight and unsprung parts have, and the suspension travel is determined to require a certain amount of damping, which can be divided between the compression and return. On a typical passenger car has been chosen to be less in compression and more rebound damping, since hard bump gives uncomfortable ride. For a sports car we use more of bump and decrease slightly in return for retaining the grip after an uneven ridge in the road as you drive faster.
The damper may have separate adjustability for high and low speed dampening, where high speed is for bumps and wheel movements while low speed setting is for chassis roll and the weight of the sprung mass. One might think that there is a lot "secrets" in the buissnines, and sure there is, but this is not so much about shock technology, but more concerning "team secrets of adjusting". When I is sorting out shocks for a race car, I set up the car in a "shaker rigg" that shakes the car while I observe things. This is far from secrets, just a lot of work.
Regards
Goran
RE: The black art of shock damping ?
Yeah I understand quantifying what a driver desires is difficult for the driver and the shock supplier. Your comments mirror my limited experience with shock adjustments. I just didn't know if once you quantify the required damping, how much comfort can be dialed in to achieve that rate via "black art".
RE: The black art of shock damping ?
RE: The black art of shock damping ?
I recently read the book Advanced Vehicle Dynamics and Damping by Jan Zuijdijk. It's an interesting read and I understand he's working on a book that's geared more toward engineers and academia.
One of his approaches that appears less common at least in the racing community, is to use more compression damping in the < 2"/sec. velocity range to improve traction. His experience using more low speed compression damping and less rebound seems to work for a variety of applications from SVO Mustangs to F1 cars. While it is perhaps 180 degrees from what many engineers have been taught and use, there appears to be some logic and results to support his approach.
I will be testing both approaches on track soon to see what works for me. Interestingly drivers reported improved ride and traction with the increased compression damping < 2"/sec. Jan concludes that with much better control of the unsprung mass, rebound damping can be lowered thus improving tire contact with the road vs. using higher rebound to control traction.
As long as you're not stunning the tire on turn-in it seems like a reasonable approach worth pursuing. Ohlins, Moton and others seem to use a similar approach as far as the increased compresssion damping < 2"/sec. from the force vs. velocity graphs I've seen though they may use more rebound damping also?
RE: The black art of shock damping ?
However, for starters: http://www
AND:
http:/
It really is not "black art". It is very time consuming and entails a lot of "chasing your tail" to get close. Close, cause I never seem to get it "perfect" !
Rod
RE: The black art of shock damping ?
Yeah I've had all of Carroll Smiths books for years. He is an inspiration and a very wise engineer.
For the record Jan who needs a simpler last name... Zuijdijk who started with Koni in the 60's, worked with Carroll and many other notables, on race car development. Jan and a fellow engineering college at Koni developed the first externally adjustable Koni hydraulic shocks. It seems like a lot of Koni engineers eventually started their own racing damper companies. We're fortunate to learn from their experience. With 50 years in the game you qualify to be writing books too if you haven't already. I read many of your comments in the 52 pages of TIPS here and I learned from them all.
RE: The black art of shock damping ?
I contacted a mfg. of performance shocks and inquired about the usable strut/shock strokes for one of their production kits and they refused to answer. It turns out that the strokes are too short for the application, which was independently confirmed. The performance aftermarket has some real characters in it.
RE: The black art of shock damping ?
RE: The black art of shock damping ?
RE: The black art of shock damping ?
Goran
RE: The black art of shock damping ?
As to brand names, I do have several "modern" brands that seem to work well...but...I prefer Koni since I have nearly 50 years experience with them.
Rod
RE: The black art of shock damping ?
Rod - I hear ya on working with people you know and trust. I too am of that age and I have no problem what so ever paying for quality products and customer service. I just walk when the seller is evasive as this mfg. was.
RE: The black art of shock damping ?
We may be in the same age, all of us here, I am myself 66, so our experience is probably a common denominator.
Goran
RE: The black art of shock damping ?
I realize that ligher is nice but I sure can't tell the diff in ride quality between a coil spring that weights 4 lbs. vs. one that weighs 5 lbs.
RE: The black art of shock damping ?
Cheers
Greg Locock
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RE: The black art of shock damping ?
I should say that EVERYTHING should be as light as possible since the sum of all savings will be great. And especially unsprung, and rotating, parts are important.
To see if things are important, we must look at the specific car as a whole.
Goran
RE: The black art of shock damping ?
RE: The black art of shock damping ?
Heavier wheel/tyre/brake rotors certainly measurably and even noticeably impacts on acceleration if it's a few kg per wheel, well at least in my experience.
Regards
Pat
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RE: The black art of shock damping ?
The argument that we do not feel difference is not so successful, there are no large weights to be removed from an already light car, but about many small things together.
Every single detail is not possible to detect by driving that it was removed, and the action would in that case have been unnecessary. Anyway, you can see it with the timing clock or other measurement tools.
Goran
RE: The black art of shock damping ?
In theory 1/2 the mass of the spring is sprung and 1/2 unsprung. As I said before I understand that lighter is better but I want to see the difference in track time for a spring that is .08% lighter in unsprung mass and .01% lighter in sprung mass... <LOL> If a driver can deliver better performance with that slight change and no other they are in a league of their own - far beyond F1 IMO.
RE: The black art of shock damping ?
Goran
RE: The black art of shock damping ?
RE: The black art of shock damping ?
That said, all else is rarely equal. The actual rate can vary significantly from what is specified. Even the linearity can vary within the stroke of a single "linear" spring.
He may have felt a difference, but it was likely due to some other factor.
RE: The black art of shock damping ?
I'm a big fan of blind A-B-A testing for subjective opinions. Much of the testing I do requires considerable thought on what I am actually experiencing and the cause. It's interesting work but I'll be damned if I can feel a 1 lb. difference in upsprung weight even though I understand the physics involved. :>)
RE: The black art of shock damping ?
There are hardly any marginals in order to get the most out of the car for a specific condition.
If I , for example, mount softer front springs then, I will probably notice that I will be grounding the splitter during braking. It is a big difference with a more normal street car where ther are a LOT more room given to spring travel to cope with different sort of situations.
Goran
RE: The black art of shock damping ?
RE: The black art of shock damping ?
Goran
RE: The black art of shock damping ?