GC Coilovers - Underdamped

[shorthand]

Well, I have had a fascinating time installing the GC coilovers. The install was straightforward though a decent amount of hard work.

The corner weighing was fascinating - a car scale is a really neat toy for a physicist. One invaluable tip was to disconnect the swaybars during corner weighing and then use washers so you reconnect them neutral. (Mine didn't need washers).

However, damping with the KYB AGX's has been a little less than ideal. I'm not quite sure what gets adjusted on the AGX's but I started out on full hard. Interestingly enough, this catapulted me into a severely underdamped situation - the car would bounce badly on the highway. It was well and truly nauseating.

GC talked some sense into me, and I started turning down the damping - and lo and behold the ride got much better. Appearently, overdamping on the fast compression (bump) and perhaps also the rebound would transmit energy into aforementioned nauseating eigenmode of the suspension. Turning down the bump damping kept the bumps as bumps, above the nausea threshold (and also much less energy in the car body period).

However, the nauseating eigenmode still exists. The car is still underdamped on slow compression - I'm just not feeding as much energy in to that mode, so the ride is more than bearable for commutes. This means that damping is far from ideal.

What I am looking for is some assurance that the Koni Yellow or some other shock will be adequately (and hopefully adjustably) damped in slow compression, so that I can better manage my Autocross transitions and so that the ride is better.

[CivicEx1998]

How low do u have ur GC?

I have GC and Koni yelow. Looking under the fender, i can see the bumpstop and top polybusing about 1 inch of travel. This is with the bumstop cut in half.
My car used to be riding on bumstop (uncut) and the ride felt really bouncy even with different koni adjustment.
Once i toke care of the bumpstop, the ride is alot better and stable.
U might wanna take a look at that.

[shorthand]

Drop is 1 -1.5", which is actually a little more than I wanted, but the cambers seem right. (The fronts are as high as I can make them.)

I'm sure I'm not riding on the bumpstops - one piece of evidence that I can cite against this is that the ride improves with suspension adjustement.

[Daemione]

Standard Koni's only adjust rebound, not compression - which may be a good thing for you. You can get them converted to adjust both, but it's not cheap.

What spring rates are you running?

[PseudoRealityX]

Originally posted by Daemione
Standard Koni's only adjust rebound, not compression - which may be a good thing for you. You can get them converted to adjust both, but it's not cheap.

What spring rates are you running?

I believe he's running 300 front, 275 rear. If you talk to koni, they can valve them correctly for compression the first time. Then you can use the rebound adjuster to your preference.

[shorthand]

300F, 275R is correct for the spring rates.

Ahh - I am now beginning to understand what is truly involved to do this right. I see now that there are no short cuts when it comes to suspension. I guess I should have known this, but that's the way it goes.

I will price up the custom valved konis and perhaps a few other options (Advance Design?) and see what I'm looking at. (Cost to upgrade to custom valved konis is $1100 as far as I can tell, and I can expect to get may $200 back for the used KYB's.) I may decide to back down to the stock springs and cut my losses at these prices.

(Perhaps I just back the spring rates down and get longer springs - perhaps 200F and 180R. At least I have the scale data to let me know how to correlate spring rates to additional length.)

Thanks again for your help.

--Stephen

[PseudoRealityX]

well, Nathan Whipple (Solo-X) is running 600# springs on his stock koni yellows and is pretty damn fast. I think Konis will be fine. Call up TrueChoice as well, and talk to them.

[Poboy]

If you've got 300, 275 for rates the off the shelf Konis should do fine, as should the AGXs.
Here's some tips from Koni's website for dialing in stiffness. Should apply to the AGXs too.
http://www.koni-na.com/roadracing.html