bgoetz

I spent a bit of time a few years back autoxing and doing some HPDE events. I ran a civic with a basic coilover that had no adjustment and got it to a decently drivable state by swapping in sway bars, springs, and race tires. I then had a stock S2k that I messed around with a bit, but that is the extent of my experience. I understand a little, but more so with regards to what I am looking for in how I want the car to feel as opposed to getting it there. I just picked up my 2nd S2k, a 2001 that has Koni yellow GC setup. I have no intention of ever swapping these out as they are basically new, so I am going to work with what I have. The shocks are rebound adjustable only, the previous owner had them on full stiff, which made the car feel like a pogo stick, it always felt unsettled. So I have been slowly gravitating towards softer, which seems to make the car feel more stable. My question is this:

-From my understanding rebound only affects the rate in which the shock returns, the higher the rebound the faster the return. A rebound adjustable only setup does not have the ability to adjust anything with regards to compression stiffness, it is what it is, unless I go with different springs. With that, once I find the spot where it feels like the shock rebound and current spring setup work in conjunction, there is no need to adjust rebound regardless if I am on the track or on the street because this spot should be the most desirable setting regardless. Or is there some reason I want more rebound on the track or autox course? I guess I am just looking for a better understanding of how to "tune" a rebound only setup.

bgoetz

Note I do understand spring stiffness and shock compression are not the same, I just don't have another way to adjust how stiff the car is since I have no actual compression adjustment.

CKit

Track, street, autocross and bumpiness of the lot will determine what your rebound settings are. They may be different depending on what you are doing. It's not a set it and forget it based on spring rate.

bgoetz

Ckit, so would you say a smooth autox type setting may demand a higher rebound as opposed to a bumpier road course setting

recnelis

Rob has collected a bunch of good information on fine tuning shocks on his website. It's one place to start out.

Autocross is highly transitional, so generally that would result in more rebound than a road racer might use. This is not a rule of thumb though, as there are different ways to approach shock tuning (discussed here in various threads and elsewhere). Ultimately, surface conditions and driver preferences will dictate how much is right.

If you feel more confident in the car and it's handling the way you want with the rebound turned down, then I'd say you're heading in the right direction.

-=Zeqs=-

Autocrossing tends to have lower speed, but tighter, transitioning turns on smoother surfaces, so it one would typically benefit more from a higher rebound than that of a someone going on a higher speed road course, where they might not want a setup with too much rebound, as they want to be able shift and hold weight in various corners due to longer, higher speed turns.

Again, as ckit already brought up, there is no "one-setting" fits all. My settings change between BW 13CW, SOWS, and CVR.

tcjensen

Surprised no has corrected a basic misunderstanding - the higher the rebound, the higher the rebound DAMPING, meaning the SLOWER the return the full length. Your shocks will have a bit of "cross-talk," meaning that stiff rebound damping will result in slightly stiffer compression. Just slightly, but from my understanding the compression will not go completely unaffected, even though that's the idea with a single adjustable shock. If what you are driving on has multiple bumps, with too stiff a rebound setting, the shock may not return to full length before the next bump, resulting in "jacking down" onto the bump stops and creating a tough ride and bad handling. So like Ckit said, it depends in the surface, how stiff you can get away with. Also helpful to remember is that shocks work mostly in diagonals, in different phases of a corner, and the traction at one end or the other is often determined by how much both tires at one are pressed into the ground. For example, as you turn in coming off the brakes, your car is accelerating and turning, so weight is moving backward and out. So the inside front is working in rebound and the outside rear is working in compression. If you car is failing to turn in well, them softening front rebound will allow the inside front wheel to extend further and press into the ground more, giving you a higher % of your front 2 tires on the ground, lessening the understeer. Note: if you trail brake into the corner ... Different story and different approach, because now you are decelerating while turning, so shocks are working inside rear to outside front. It's a crazy balancing act

Slowcrash_101

To tune suspension you take measuments of tire temperature, the goal is to make the tire temperature as consistent as possible on the inside middle and outside shoulder. You change damping, spring rates, roll bars, alignment, and tire pressures first to hunt for even temperatures. Then you fine tune for balance to improve feel and confidence.

Forcednduckshn

^^^What this guy said I read the post and didn't say anyting since I figured someone else would and I was busy

One thing to add regarding rebound in the front is you may get second order influencers on grip that may actually add grip when increasing front rebound. These includes a little more weight loaded over the front wheels for a longer duration of time as the nose tucks in, in addition to keeping the wheels cambered more for a longer duration of the corner (more suspension compression = more camber gain) and more dynamic toe out. If you see some tuning guides posted on here (for example, Jon Lugod's) he lists adding front rebound as a tuning solution to mitigate mid corner understeer. Just something to keep in mind that there are multiple influencers acting on cornering grip at different phases of the corner, for different reasons. In the end, you need test adjustments, understanding how the impact the movement and operation of the suspension and move forward. I have experienced the addition of more rebound in the front and rear to have both understeer adding and oversteer adding effects, depending on the rest of the setup of the car and conditions. These same "Second order" influencers apply to other tuning methods, like swaybars. Though in particular for the s2000, the double wishbone design really relegates bars to affecting balance in one direction - more front bar having the effect of adjusting the balance of the car to add rear grip, while rear bar would have the opposite effect, etc..

bgoetz

Hey thanks for all the advice guys and for setting me straight, this will be really helpful as I move forward!