[4banger]

Originally Posted by stretch

The car feels a little underdamped compared to what I'm used to, but I keep thinking of Dennis Grant saying something to the effect of almost all sports cars are overdamped. Since car control is already very good in this setup and both grip and ride quality are equally superb, I have no real motivation to try stiffer settings.

Stretch - I've still been searching for where you want your dampers to be critically damped at: compression or rebound. Still no luck. Compression will always be way overdamped with your spring rates(your at 88%, so hopefully compression isn't where you want to be at .65critical), but rebound could easily be adjusted to 65% critical damping. Right now my calculations estimate that you are at 50% critical damping, so going a touch higher may help. It would be very interesting to see what you thought if you ever get a chance to increase the damping on the rears a bit.

Also, I saw in a previous post of yours that you had found some generic dust covers to try out. Did those not work, or do you still plan on trying them out in the future?

Thanks

[stretch]

It's definately rebound. It's fairly common practice to have very little bump resistance in the rear, illustrated here (Ground Control / Koni coilover dyno for BMW):
http://e30m3performance.com/tech_art...rear_shock.htm

[4banger]

Thanks for the link, Stretch. Great find.

[waktasz]

I was just quoted $1999 shipped for the full setup + front camber plates only with SA Konis . Now I'm really going to have to think hard about these or the RCE. And get another jerb.

[stretch]

Well, if money is an issue, you can save $300 by using WRX housings for the rear and using off-the-shelf Koni 8610 inserts. That's what I'm doing, but you already knew that.

$1999 is $250+ less than RCE's setup, but that's a small enough difference that it would indeed be a touch decision.

[waktasz]

It's not that much of an issue...just means I won't be fronting the cost while I try to sell my Zeals. The $1625 price with camber plates posted in the first post was a bit misleading until I read a little closer. Maybe I'll just give my Visa a workout this month .

[stretch]

An update:

Coil binding in the rear:

My rear springs (8" long, 250#) reach their solid length at 3 inches. I have about 2.6 inches of bump travel before binding, so I don't think I'm experiencing coil bind often, but my bump stops are very short and do not engage early enough to prevent the spring from reaching its solid length. The problem is the location of the upper spring perch: it fits over the "dust boot holder" on the stock tophats, which makes it way lower than the end of the strut travel. This might not be a problem if the lower spring perch was also lower, but lower spring perch does not go low enough unless you trim away the stock lower spring perch (which gets in the way of adjustment).

If you're running Koni's in WRX housings in the rear, I recommend cutting off your stock lower spring perch. If you don't, it gets in the way and prevents you from lowering the Ground Control spring perch more than half way. The problem with this is that you set yourself up for coil bind, as a fully compressed spring will have no where to go. If you're running Koni's in WRX housings, make sure you choose your springs and ride height such that you have the rear spring perch almost completely at the bottom of the sleeve.

Personally, I haven't done this. I'm breaking my own rule because I haven't found coil bind to be a frequent problem in real use. There's enough suspension travel back there to make the problem quite rare. I'd like the ability to switch back to the stock springs and still use my Koni's, so I'm not eager to cut off my stock spring perch. I may be forced to, though, the first time I try carrying a wife, two dogs, and a trunk of luggage through a construction zone. Coil bind isn't fun. I switched back to my soft, stock strut tops so that there's some rubber to deflect in the event of coil bind.

In any event, this is definately a setup-dependent problem that not everyone is going to have. Choose your springs wisely so that you can run your lower spring perch as low as possible. Don't run off-brand springs because they tend to have a longer solid length than Eibachs. Also, because of the different top hat and lower spring perch in the Ground Control housings, they absolutely would not have this issue. This issue is only for those running WRX or STI housings, only in the rear, and only after an unlikely amount of suspension compression.


Progressive springs?

Ground Control (specifically, Mark) says my springs are linear, but I don't see how that could be. At my ride height, three "soft" coils are just about fully compressed whereas the other coils are barely compressed at all. My springs are indeed the initial spring rate I ordered, though, because they support the weight in of my car in exactly the amount of compression I'd expect them to (about 2.8 inches). See the picture:



So, if they're progressive, and start out at 315lb/in, what do they go to once on the firmer coils? The coils are almost twice as far apart, does that imply twice the spring rate? I hate progressive springs, they cause nothing but trouble. I'm finding that I can't find an ideal damper setting for my shocks. The car gets a little light from having too much rebound when cresting over bumps, but is clearly underdamped when rebounding off of a big compression. It actually tests very similar to a stock STI suspension in that regard (but is ultimately more comfortable due to no bobblehead, more bump travel, and softer bump stops).

Perhaps that's just me hitting the bump stops, perhaps not. I've got 3/4 of an inch before hitting the bump stops on my current ride height which (because of how soft the GC bump stops are initially) should be sufficient I think. Or, maybe the shock valving is junk- but the only GC-spec Koni dyno I've seen looked quite good.

My bet is on these springs being sharply progressive. They're springs made specifically for Ground Control by Eibach, as Eibach doesn't normally make 9" long, 2.5" diameter springs to my knowledge. I guess my current recommendation is to avoid them until I can figure this out.

Overall, I am happy with this setup. I'm just not overwhelmingly happy. I'm pretty sure my standards are much higher than what you find elsewhere on the Internet, though, so keep that in mind.

I tried calling Mark about this but he's on vacation this week. Until then!

[ButtDyno]

Are those the "barrel" springs in the rear?

[lackskill]

sounds like a mixed bag of worms. Some good, some bad. I hope you can get it sorted out.

[stretch]

Nope, they rears are totally straight. They're normal Eibach springs.

Mark said those front springs (pictured above) are barrel springs, but if they are, it's very slight. I never really took the time to examine them as thoroughly as I should have, I guess, prior to installation. Nonetheless, the "soft" coils are clearly compressing faster than the others so this must be a progressive spring. Mark did say there was a very minor progression to it (all springs are mildly progressive really), but this looks more than minor to me. They're labeled as linear springs, though- the printed "55" number would be hyphenated with another value if they were progressive. I'm rather confused.

[4banger]

Maybe when you talk to Mark, you could also get him to throw out a few low speed damping numbers.

[stretch]

I did ask someone at Ground Control about a Koni dyno. The rep said they only have dynos of their Advanced Design shocks, not of the Koni's. Of course, that's rubbish- they must have them somewhere. I wonder if I was talking to the same guy who told me they didn't sell STI Koni housings. I'll ask again when talking to Mark.

[thrlskr]

Then they should dyno some of the konis they have lying around. Thats just a useless response.

[Tim Flat4]

These numbers would be extremely beneficial.

Stretch, does it bother you how vague the dampening adjusting is on the Konis? I know it bugged me when I had them on my RS.

[stretch]

You mean how the adjuster doesn't have clicks? No, not really. I can count how many times I've turned the knob just fine.

On the other hand, it does bother me how half a turn at the soft end makes no difference, but half a turn at the firm end is pretty extreme! The adjuster isn't linear at all.

Still, I don't consider that a huge issue. Once I settle on my final damper adjustments I'll never touch them again.