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Ground Control Lowering Kit

Thanks Dreamin

Ground Control has successfully built a coil-over kit for the V! Front and rear drop of 0" to 1.2" +/-. Your choice of spring rate (they have recommended rates). Kits work with stock shocks (FE4 or FG2) and will come with custom rear shock mounts to 'fool' the load leveling. Production kits will be available Jan 4, 2006. Price will be $499.

A prototype kit is installed on my car. And I couldn't be happier with it; it's working very well. Their goals were to improve handling (by both lowering the car and using stiffer springs) and not increase noise... they succeeded in both.

  • Front:

    Front setup is very straight-forward, attach threaded spring perch onto the shock body, use Eibach 2.5" coil-over race springs, new top shock mount was built w/new bump stop.

  • Rear:

    GC choose to use the stock rear spring mount points... they said switching to a conventional spring-over-shock coil-over would have changed the suspension geometry too much. And my concern with this would be, without lots of data from GM, there is no way to know if the shock towers are strong enough to handle the weight of the whole car (esp. over the long term). Custom pieces were made for the top and bottom mounts, the height adjuster is up top, again Eibach 2.5” coil-over race springs. Rear bump stop remains inside the rear shocks.

  • Spring rate:

    They tested a lot of springs: 450lbs, 500, 550, 600… front and rear combo’s (It sounded like building the kit took less time than testing spring rates) For the FE4 shocks, they are recommending 500lbs front and 450lbs rear. GC testing determined that the front FE4 shocks cannot handle more spring than 500lbs… and handling was more balanced with 450lbs in the rear… the shocks can handle 500lbs, but they said they weren’t happy with the “rear wheel frequency” and “the rear didn’t stay as planted” with the 500’s. They need to test the FG2 shocks and will come up with recommended spring rates… they think the FG2 could be pushed to 550-600lbs!

  • Ride Height:

    GC determined that the car is most balanced at 26 7/8” front and rear ride-height - ground to fender lip… (they use suspension based measurements, the 26 7/8” is my translation of their numbers). On my car this was a 0.70" front drop (w/0.5" more possible) and a 0.95" rear drop (cant go too much more with the WW spacers on my rear shocks). I have no rubbing at this height (stock wheels / tire in front, stock wheel / 275s in rear). They said, flat worked best, as all the frame to suspension measurements are the same front-to-rear, meaning the frame is now flat. And the car corner-weighed the best at this height. They did research the car’s stock rake… they believe the stock rake is not for handling, it was done for aerodynamics (fuel economy?)… But with a coil-over setup, you can setup the car for what works best for you! For whatever reason (shape of rear fender?)… with the car flat, it looks lower in the rear to me (though the tape measure says it’s not)… I’m not sure if I will raise the rear (just a hair) or not.

  • Noise:

    All springs have urethane mounts top and bottom for noise suppression. Where the stock mounts/bushing were deemed stiff enough they were reused, where they were deemed too soft, custom bushings were made. End result is no noise from the front, and a slight increase from the rear… only perceptible with the radio off. I do have a small squeal from the left rear, I have to talk to GC about this… only one corner is making it.

  • Road Feel:
    Far bigger difference than I thought!
    High-speed floatiness – Gone.
    Front-end nose dive on hard braking – Gone.
    Right/left body sway on uneven pavement, leaving driveways, etc. – Gone. (It feels like I installed stiffer sway-bar.)
    And the biggest difference is in steering response… it’s so much quicker now… I didn’t think it would make as big of a difference as it does.

  • Ride:

    The ride is a little stiffer… you know something has changed… but it’s definitely not too stiff. FWIW I asked the wife if she felt a difference… she said no. Given my car is 80% for road-trips, 20% for road-courses, I did not want too stiff a ride… thus my concern w/500lbs spring in some earlier threads… I was wrong… 500lbs is not to stiff… it’s *just right*. Going over pot-holes, freeway expansion-joint, etc… it’s definitely a *bam* now, instead of a *thump* or *whoosh*, but the ride is not harsh at all. (Yes, it’s hard explaining ride quality with sounds) I don’t have FG2 shocks, but from the threads here, I think ride gets harsher when upgrading from FE4s to FG2s vs. the stiffer springs I have (just a guess obviously).

  • Handling:

    Unfortunately it’s been pouring rain since I got the car back… so I haven’t fully wrung out the car . But on semi-dry roads, driving 7/10th, the car feels very balanced, I thought is would understeer with the 500/450 springs, it does not… things definitely happen much faster now… more handling feedback once it drys up a little.

  • Shocks:

    GC was very familiar with the V shocks, the “regular” and “performance” models. They said both shocks were very well designed, and Sachs put a lot of R&D into getting the valveing right. They highly recommend using the factory shocks (FE4 or FG2) with this kit. I asked about Koni and Advanced Design. They said they would work with Koni on options… but said Koni has been very difficult to work with lately and extremely slow. About AD, they said “that’s really a race shock… given that you have to rebuilt it, etc… it would not be a good option for this car”. I got the impression we shouldn’t hold our breath for aftermarket shock options. For you guys who absolutely want an adjustable shock… I suggest you call GC directly (talk to Jay or Dale) and put a bug in their ear. And someone with QA1 shocks should definitely talk to them… I think the only change required would be the front shock threaded sleeve (?).

  • Fooling the rear shocks:

    GC will be making a new top mount for the rear shocks… they think they can get a 1.2” drop from the rear with their mount. (Max drop is closer to 1” with WW’s mod.) They are *trying* to come up with a mount that comes apart and adjusts from the bottom… so you only have to remove the rear seat once (to install their mount) and then any future spacer adjustments don’t need seat removal.

  • Availability:

    The kit will include all coil-over hardware, 4 springs (you pick the spring rate, or go with their recommended rate), a custom tool to pop out a bushing from the front shock mount which is reused, the new top mount for the rear shocks, and a giant Ground Control sticker for your windshield (j/k ) They have all parts but one in stock… they should have that in by Jan 2… So they believe they can start shipping production kits Jan 4, 2006. Pricing for the kit: $499. GC will be doing a Group Buy to kick things off... They will be joining as a supporting vendor... until then, that's all i'll post on this.

  • Finally:

    When I went to pick up my car, they had washed it... and apologized if my radio presets were lost as they had to remove the battery... I tell you... it's the little things that make your day...

    2 thumbs waaay-up for the coil-over kit, and Ground-Control as a company.


    On the road:


    Front spring perch:

    Front top mount, new bump-stop:


    Rear, very bottom mount:

    Rear, top of bottom mount:

    Thanks Dreamin!

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