Does this logic make sense?

NOTES
1.When changing to firmer springs, the shocks usually need to be set firmer for rebound and softer for compression damping.

This is from the Koni Motorsports catalog, tuning section, pg 16.

http://www.koni-na.com/pdf/KONI_Motorsports_2008.pdf

Obviously it is over simplistic, but is this solid logic?

 

Thats the general consensus

 

It's hard to give generalizations but stiffer springs would probably need more compression as well to damp the resistance of a heavier spring. Then again it all depends on the goal to begin with.

 

Koni basically has it right, if there are no other variables.

Billy, I'm scared to disagree with a legend, but I think you would only need additional compression if you had a theoretical setup that allowed the damper to "pull" on the spring and stretch it beyond free length, thus necessitating compression damping to control return to free length. I've never heard of a setup like that though.

 

That is true only if you not changing anything but spring.
If you would revalve as well it would be different story, as Bill say.
There is no number set in stone how much damping you should have, just base line. From there you change it as needed for your application.

 

If you have damping that's optimized for a given spring, then install a stiffer spring, the generalization is correct. Under compression the spring rate and compression damping is additive. If you had it optimized before, it will tend to crash/skip over bumps due to the additional total resistance to compression. On rebound, the spring and shock work against each other. If your rebound was optimized with the old spring, it will offer too little resistance to the stiffer spring and will not adequately control rebound speed, and will tend to "launch" the car over bumps.

 

So is the reverse true?

If I have a shock with a fixed compression valving and adjustable rebound valving and variable spring choices. This is true of a lot of setups, where the variables are spring rate and rebound damping. So lets set aside rebound with the assumption it can be adjusted to a range of springs. With regard to choosing spring rates if I go from softer to stiffer spring rates progressively, does this mean the compression damping effectively goes from under dampened (low spring rate) to over dampened (high spring rate)?

 

Man, a lot of over thinking this lol If im understanding you correctly, yes that is right. If you think about what compression damping does, in simple terms, it is a hydraulic way to control the upstroke of the suspension, just as a given spring rate would do. They do these things through different measure/technology, but the net result is much the same on the upstroke side. So naturally if you are increasing one of these avenues, yet want to maintain the desired compression control as before, then obviously you have to back off on the other.

So, when moving to a stiffer spring rate, less compression damping is required, but more rebound is needed. When moving to a softer spring, more compression damping is needed, and less rebound.

Now for us single adjustable damper guys, we obviously will be making some level of compromise when moving to different spring rates.


If anyone wants to throw in some more external factors to make this more complicated, be my guest.

 

^To counter that theory most race cars for the last decade or two have been running compression biased damping even with downforce cars and the resultant insane spring rates...

 

I don't find this statement very helpful.

Anything an aero car does, is irrelevant to this discussion as well.