I'm having a hard time understanding how damping rates affect balance...
I see and hear somewhat expirenced people (all the very good people seem to have their car sorted before they show up) at autocrosses talk about how they change the balance by stiffening/softening shocks, but my confusion is that it does not seem like stiffening/softening a shock would have the same effect as increasing/decreasing a spring rate, but that is how it seems people are useing them?
I participated in a thread in which someone mentioned transient response, and how shocks control the speed at which weight is transferred, while springs control the amount of weight transferred, but I don't understand how that would affect balance.
So how does changing damping rates effect balance, and where is a good starting point for koni yellows on H&R sports on an ITR on Azenis in STX? (that was a mouthful...


[Modified by tecnic1, 11:13 AM 10/11/2002]

 

hmmm....I'll let someone else open this technical can of worms before I put in my two cents!

 

well, since no one else has offered any explanation I'll go ahead and give you my hack autoXer perspective on the matter.

think of a spring as a bouncing ball, you drop it and it continues to bounce until all of it's potential and kinetic energy has been used up. that represents a spring alone.
now imagine dropping that ball in a shallow puddle, doesn't bounce as high and as often does it? the puddle absorbs some of the ***** kinetic/potential energy.
the puddle represents the damper.
when they talk about stiffening their shocks at autoX, imagine that as making the puddle you are dropping the ball into deeper. The deeper you make it, the less the ball bounces.
that's how shocks work to control the movement of the spring. what actually balances the car is the spring, since that determines how much the car will roll in a given turn. to eliminate body roll, naturally you go with a higher rate spring...when you increase the spring rate, imagine that as moving to a larger, more dense bouncey ball. Naturally, you'll need to make the puddle deeper to accomidate <sp> the bouncier ball, which translates into correctly valving the shock for the higher rate springs. Otherwise you end up with a shock that can not handle the spring, and the spring will ocsillate (bounce) more freely.

i hope that helps, sorry for the crappy bouncy ball in a puddle analogy, it was the simplest one I could think of

 

i dropped a bouncy ball in my toilet and i cant get it out.
it didnt bounce.

 

here's a intro on dampers from my old PBH site.

http://www.g-speed.com/pbh/dampers.html

 

http://www.tripointengineering.com/Koni/koniTune.htm

This link is a general guide line on tunning your damping rate...

Adjusting your damping rate only affects transient response so it will affect intial balance of the car. For instance rear stiff and front soft will promote turn in oversteer and rear soft, front stiff will have initial turn in understeer... As you gain more and more experience you can differentiate half a turn on the damper and how it affects the car.. In addition to that driver feel is also very important, my off the shelf Koni yellow dosen't generate enough low speed bump force hence making the car feel numb at higher speeds.. On my 400F, 300R spring set up I have to max out my rebound setting to make the car stable on the track...

Charleston


[Modified by CivicFerio, 7:08 AM 10/11/2002]

 

Dampening: to make damp.
Damping: to diminish the activity or intensity of.

Just a correction so that nobody bites your head off in the future.

 

As mentioned previously, springs act on displacement (F = k*x ) while shocks act on velocity ( F= dampingconstant*v ). So shocks don't do anything unless the car is rolling or pitching (or bouncing). Once the car has settled ino a steady state situation, they do nothing. But what percentage of an autocross do you spend in a steady state condition?

While the car is pitching or rolling, the stiffness of the shocks behaves the same way as stiffness in springs, and the sum of the two effects (among other things) determines the balance of the car during transitions.

 

hrmmmm.....so since I'm happy with the car's balance on the current setup (aforementioned H&R sports and stock shocks), except that it tends to feel unsettled, I want a bigger mud puddle (stiffer shock settings)? But, would that cause it to transition to either understeer/oversteer in a less progressive mannor? I really like the way the car feels under brakeing, and I don't want to compromise that too much.


[Modified by tecnic1, 11:43 AM 10/11/2002]

 

I'm assuming that you've messed around with your shock settings? if by unsettled you mean that the car rolls during transitions, dives under braking and squats under power, then you need to go to higher rate springs....the shocks can't control the weight of the car, that's the springs job...all the shocks do is control the movement of the springs.

 

What I don't think anyone has said yet is that a few tests are worth a thousand words. Set both ends full soft and do a run. Then set both ends full stiff and do the same. Repeat with one end full stiff and the other full soft, then switch. You will know have bracketed all of the extremes possible within the range of adjustment that you have. Keep track of times and you will have some empirical data to compare with your butt-dyno readings.

Start with the option that seems to have the most promise and tweak it from there. Use baseline tire pressures (and don't change them or anything else between tests) and then do your final tuning with different pressures, after your shocks are close.

There are just too many variables to be able to compare your set-up with anyone elses, so rely on your own information. This will mean that you might throw a couple of run times in the process of figuring out what is up but maybe you can enter another class at your next event, or do a non-points event if you care about your finish.

Kirk



[Modified by Knestis, 8:39 PM 10/11/2002]

 

nope...never had adjustables before. Don't have them on my car yet...
The issue with just goofing around with them is that the koni yellow rears for the ITR are not externally adjustable. I could work something out though.