Ground Control Coilovers Review

[donoman]

I got GC's street/school kit with 375 lb/in and 440 lb/in rear. Got the street camber plates too, because didn't want to deal with a spring compressor. Priority was to lower the car a bit but still retain ride quality. My car may never see the track, but I want it a little lower and wanted the adjustable shocks to dial in the right ride quality for the stiffer springs. I looked at different kits: KW V3, KW Clubsport, TCK. KW seemed to have a good consensus but more expensive. TCK seemed to be known to be noisy. GC had mixed reviews.

Service:
Talked with Mark at Ground Control, awesome guy, awesome service, we practically talked for an hour just shooting the shit. Initially, I just wanted to call and get some info. By the end of the conversation I felt like this guy was so cool, so I took my credit card out and made the order right there. I'm glad I did.



Installation time:
Installation took me about 5 hours, with a lot of time spent trying to find my wheel chocks and figuring how to get my jack under the car. I would say it's a simple installation if you have a friend to help out. I did use air tools to break some bolts free, so your mileage may vary. My electric impact wrench was not powerful enough to break some suspension bolts. Blue locktite on everything on reassembly.

Ride quality:
Front rides well. Very nice and compliant.
Rear was way too bumpy at first. I might have adjusted the ride height too low because it felt like I was on the bump stops. The first thing I did was dial down the damping and that helped a lot. Then I raised the car about an inch and it helped tremendously with ride quality. I was rubbing on hard sweepers but raising the height helped a lot. I'm not sure if I'll need fender mods, but probably, because I'm running a wide rim in the back.

Noise:
No noticeable noise on the street, but some clicking when going over driveways or speed bumps sideways. Retorqued shock mount nuts last night with the wheels down, will see if that helps. Could be my sway bars but I did torque them to spec. Maybe I need to torque them more.

Adjustability:
Rear adjustability is done with a spanner wrench and is a pain in the ass. The wrenches come with bottle openers, which are cool, but could probably cut you if you slip, so this requires extreme care when raising ride height (it's easier to lower ride height). I just used a glove.
Front adjustability is a freaking piece of cake. You don't even need to remove the wheel to get to the spring collar.
Camber plates are VERY nice. I'm glad I got them and would say that they are a beautiful piece of work.



Instructions:
Suck. Non-existant. Need to reference E46 forums for info on this. Luckily it's all very straightforward but some diagrams showing the order of washers, the orientation of rear shock mounts etc would be very helpful.

[dorifto88]

looks good! if you want a set of works mine might be up for grabs lol

[The HACK]

The noise from the back is "normal." It comes from the shock internals. I've had it since installed and no matter the amount of re-torquing with the shock mounts it never goes away. Outside temp seems to affect it more than anything else (when it's hot it makes more noise).

I'm surprised you had to raise the rear. On my adjuster collar, at the LOWEST setting, it's barely the same height as OE. Raising the rear collar an inch would have resulted in a 4X4 look.

Could be I had one of the earlier kits, it's been on the car since 2008.

[3002 tii]

Those tires look really meaty lol, looking good man!

[donoman]

Originally Posted by The HACK

I'm surprised you had to raise the rear. On my adjuster collar, at the LOWEST setting, it's barely the same height as OE. Raising the rear collar an inch would have resulted in a 4X4 look.

I'm sorry, I should have clarified that I raised the wheel height was raised approx 1 inch.

I think these springs are pretty short. In the side picture I showed, I raised it already and the collar is approx in the middle of the collar.

Also, the springs don't look like a honeycomb... they look like a cylinder. Is it possible that these are not progressive? I was hoping for progressive springs for better ride quality on the street.

[Caddyshk]

Originally Posted by donoman

I'm sorry, I should have clarified that I raised the wheel height was raised approx 1 inch.

I think these springs are pretty short. In the side picture I showed, I raised it already and the collar is approx in the middle of the collar.

Also, the springs don't look like a honeycomb... they look like a cylinder. Is it possible that these are not progressive? I was hoping for progressive springs for better ride quality on the street.

My GC (Eibach) Springs are not progressive...

[Kgolf31]

Progressive springs will not give you ride quality.

Common misconception, but the money (and ride quality) are in the dampers. You can go with whatever spring you want, but if you cannot effectively dampen that spring correctly then what does it matter?

Linear springs are a better way to go, because they are a constant rate throughout the whole travel. Unlike progressive, were you get a very light spring rate which increases through travel. In a progressive spring, if you hit a harsh bump or similar, you will quickly go through that light spring rate in the beginning and hit the stiffer rate, causing a jarring in ride quality. It is also hard for a damper to control a progressive spring....well it is harder than say a linear spring.

The TCKs do make noise, but they are only in the DAs. With that being said, they make noise in the cold because of the internal fluid. Above 50F it is like a normal noise.

Enjoy the kit. Spring rates seem kinda low, but if you're just DDing they will suit you well

[donoman]

Originally Posted by Kgolf31

Progressive springs will not give you ride quality.

Interesting, what are progressive springs for, then? I view them as this equation:

F = kx = (k1 || k2)x (springs in series add in parallel)
F = (1/k1 + 1/k2)^-1 *x= (k1+k2/k1k2)^-1 *x = (k1k2/k1+k2)*x

where k1 goes to INF at high x displacement yielding

F = k2*x

this leads to a soft spring rate prior to spring 1 binding and a harder one after spring 1 binds. Damping is assumed constant with x (shock travel) but I'm guessing a lower spring rate would allow the car to soak up little bumps easier. I do understand that varying spring rates would make the car more difficult to handle at the limit.

[donoman]

Sorry, I have a tendency to kill threads when I geek out

[yousefnjr]

Looking good! The car I mean, not sure about the math lol

[donoman]

If the math is wrong I'll need to go back and revise my PhD thesis ;-)

[pokeybritches]

The spring, damper, car, and road must all be matched. It's harder to match progressive springs due to the varying rate. In theory the initial rate is made softer to absorb the small bumps, but the overall spring won't bind on larger bumps because of the rate increase. Predictability suffers and the dampers are only optimized for one point.

After comparing my stock M (progressive) and non-M (progressive with Koni S/A) to my TC Kline D/A's, I prefer one spring rate (linear) with adjustable compression and rebound. It's more controllable and there are less variables to set up.

[donoman]

The car was launching my butt into the air over big bumps. Called GC, talked to Jay and then Mark. The top adjustment for the Koni's is rebound damping... I increased the rebound damping a little bit and she rides much nicer now. Great customer service.

[donoman]

After some canyon runs with the car, got tired of bottoming out. Quick call to Ground Control and Mark asks me to send some pix. Turns out I'm bottoming out AND coil binding (didn't catch the coil binding). He decided he wanted to up my spring rate to 525lbs. This will require a retune of the rear rebound, but gotta say I'm happy with GC customer service so far.