The black art of shock damping ? 1

[TrackRat]

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".

 

[TrackRat]

Right but the difference I was talking is .5 kg on a coilover spring which is much different than the effect of accelerating a rotating mass.

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.

 

[hemipanter]

I am with you in what you say, and it is only half the spring weight. I am also with you in the respect that no one will feel the difference, or it might even be hard to detect on lap times. What I am pointing out here is that it does not matter how hard it is to detect, in theory we know that being lighter is an improvement. Therfore a light bolt is better than a heavy one. Of course, everything is a matter of time and cost so we must all take everything in to account when deciding what to do.
Goran

 

[TrackRat]

Yup we agree. The particular question came up when a person changed the springs on his coil overs and increased the spring rates at the same time, then he claimed the ride was much better with the exact same shocks because the springs were .5 kg lighter... I just laughed to myself but thought it would be fun to see if anyone here had even bothered to try and measure any diff with such a minor change in spring weight. I think we're all on the same page on this subject.

 

[JahanAssadi]

I'd be skeptical of anyone claiming to feel a subjective difference between a 4lb spring and 5lb spring, all else being equal.

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.

 

[TrackRat]

10-4 on that. I just found it funny that enthusiasts tend to experience what they want to experience... with Mods for the most part. <LOL> I think we all know that a louder exhaust or intake always makes more power no matter how badly engineered or produced?

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. :>)

 

[hemipanter]

Well, it is hard to FEEL the difference in the sence that one should be able to tell the spring rate by a few p/inch simply by driving the car. But, to speak for myself, I use no more ground setting than necessary, and I do not use more spring rate than necessary, which means that I make use of most of all the present wheel travel.
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

 

[TrackRat]

Grounding the splitter under braking is OK for some race cars but not good for the street! <LOL>

 

[hemipanter]

What I meant was that when the car is set to close tolerances, (not only the splitter) you will then notice even small effect of altered spring rate that would otherwise not have been detected by the driver. So, it is a question of the car is use to the edge of its potetial, that govern what is possible to notice.
Goran

 

[TrackRat]

Yup, understand.