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Discussion Starter #1 (Edited)
Buying
Bought these over the phone directly from Ground Control (they have actual customer service, you know, real people) which was pleasant. They ask a few questions about your intended usage, what colour you want them powdercoated, and off they go. I received them two weeks after ordering, and they were well packed. They come to your door fully assembled with all associated hardware.

Install
Installation was very easy as they come fully assembled and are significantly lower profile than other kits out there. That means less fighting to get everything installed. The rear deck removal was nowhere near as bad as some were making it out to be. Can easily be done with a friend in 6 hours. We did it in 4. TIS calls for 9, but that involves R&R of strut assemblies, which we don't do here as the GC kit comes ready to install.

Impressions
I have the street kit. Out of the box, the only adjustments I made were a few turns on the fronts towards stiff, and height adjustment on front and rear. Both the fronts and rear are running a turn or two off maximum height. That translates to a lowering of about 1" all around. I didn't want to lower the car, so this was good. I'm running -0.9* front camber and -1.8* rear which is on the aggressive end of the stock recommendations. This setup is VERY impressive. As in, better than my E92 M3 was by a large margin. The ride is very controlled with excellent damping. I have owned many setups (including Koni+Eibach, which are the manufacturer/suppliers to GC, though they use customized specifications) and this is by far the best yet. It really makes everything else feel cheap.

Turn in is very crisp and body roll is no longer easily noticeable. I was debating picking up swaybars but I will no longer be doing this as the suspension is highly competent. The front indentation (an option on the E39 M5 kit) is rather a handy feature and I'll be taking advantage of that when running my 275 fronts. One impression that I had immediately, that other people also noticed when driving it, is that it makes the big M feel noticeably smaller and nimble. Gone is the barge-like feel of stock. It has new life. From my current impressions, I would say this kit is going to be perfectly fine for a track. If you're on the fence on whether or not to get track/street, I'd go street. If you're like me, you like a BIT of give at the race track, so this kit's perfect as-is. I imagine the track kit will be very stiff.

For those of you looking for a plug and play solution, this is it. All in, to Canada, it cost me $2200. This is fairly reasonable as in order to "do it right" with camber plates and gaskets, bump stops, etc, you are looking at something pretty close to that. Remember, this is a FULLY assembled plug and play kit with all hardware (even locking nuts!)




And here's a shot of the rear deck. I got a real kick out of this one. Had to laugh at how many layers there were. Ultimately NOT a difficult job just sort of humorous.
 

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Hey Stefan,

Where 'bouts in Canada are you located? Anywhere near Calgary? If so, I'd like to check out your setup, as it is something I am considering. Let me know!

Rob
 

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Discussion Starter #4
Hey Stefan,

Where 'bouts in Canada are you located? Anywhere near Calgary? If so, I'd like to check out your setup, as it is something I am considering. Let me know!

Rob
Calgary, yep. Shoot me a PM.
 

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Nice. I have been considering this kit vs the Dinan suspension kit. Although the Dinan is not adjustable, pricing is similar. Any comments ?
 

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I have driven a car with dinan springs struts and rear sway bar with the fixed camber plates and although it is a big improvement over my tired stock it felt a tad on the soft side for my liking. This being said I have not driven another e39 with any other kind of suspension work so its hard to really compare.
 

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How does the ride quality compare to stock on PUBLIC roads? Say for example on the highway, secondary roads, and rough roads? Does it crash over bumps?

And when you say this set up is better than your E92 M3 - in what respect? Was your E92 M3 stock?

Also - any pics of your current ride height for reference?

Thanks in advance!
 

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What are the spring rates you went with?
 

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i ran the koni sports with lowering springs and it was not a good combo. way to crashy, just felt to soft/not enough compression damping. the whole car just felt loose and like to sway around. im running bilstein sports now and imo its perfect. now these konis that gc is using may not be the same as the sports you get for stock springs.
 

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Discussion Starter #11 (Edited)
Nice. I have been considering this kit vs the Dinan suspension kit. Although the Dinan is not adjustable, pricing is similar. Any comments ?
Don't see any reason to go Dinan given the adjustability of the GC kit and it's close attention to detail for E39 M5. I don't see it being a better kit.

How does the ride quality compare to stock on PUBLIC roads? Say for example on the highway, secondary roads, and rough roads? Does it crash over bumps?

And when you say this set up is better than your E92 M3 - in what respect? Was your E92 M3 stock?

Also - any pics of your current ride height for reference?

Thanks in advance!
I live in Calgary, AB, Canada. Our roads are brutal. So it's firm yet still somewhat plush and forgiving. I would certainly not characterize it as crashy at all. My E36 M3 was crashy (Bilstein/Eibach). My E92 M3 was stock and was very similar but had less overall dampening and felt more spongy. The GC kit feels firm and confident but doesn't beat you up.

No real pics yet. I did take a quick one though. I'd say it's around 0.5" lower than stock. So pretty much perfect for me. Like I said our roads suck especially in winter. It can go much lower.




What are the spring rates you went with?
430/280 (street)

Here's my invoice contents.
2017.02 E39 M5
7430 GC 180.64.75: 7 inches long, 2 1/2 I.D., 430 lbs/inch 2
9280 GC 230.64.49: 9 inches long, 2 1/2 I.D., 280 lbs/inch 2
CCPE39M5 Camber/Caster Plate - E39 M5 (Pair)
bmwmountM5 Rear spring / shock mount, BMW e28, e21, e34, e39. 2 1/2 spring only 1
Strut MacPherson Strut Housing, part of kit requires strut inserts listed below. *RED 2
1547spgc Ground Control Custom valved Koni strut insert, top adjust 2
1225spgc Koni single adjustable shock, top adjustment, custom valving 2
bumpstop Ground Control Bump Stop 4

i ran the koni sports with lowering springs and it was not a good combo. way to crashy, just felt to soft/not enough compression damping. the whole car just felt loose and like to sway around. im running bilstein sports now and imo its perfect. now these konis that gc is using may not be the same as the sports you get for stock springs.
May not? They are completely night and day different shocks. Not only are they adjustable in their damping, they are valved specifically for the springs which are ordered specifically by Ground Control from Eibach specifically for this application. Nothing is generic on this kit. That is why it's such a steal and you really can't compare it to another generic Koni strut or Eibach spring combo. It should be general common sense that lowering your car even with upgraded dampers is always going to result in a sub optimal ride. I had Bilstein and Eibach on my E36 and Bilstein and H&R on my E46. They weren't great. But I certainly wouldn't apply that judgement to, say, a PSS10 kit.
 

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Don't see any reason to go Dinan given the adjustability of the GC kit and it's close attention to detail for E39 M5. I don't see it being a better kit.



I live in Calgary, AB, Canada. Our roads are brutal. So it's firm yet still somewhat plush and forgiving. I would certainly not characterize it as crashy at all. My E36 M3 was crashy (Bilstein/Eibach). My E92 M3 was stock and was very similar but had less overall dampening and felt more spongy. The GC kit feels firm and confident but doesn't beat you up.

No real pics yet. I did take a quick one though. I'd say it's around 0.5" lower than stock. So pretty much perfect for me. Like I said our roads suck especially in winter. It can go much lower.





430/280 (street)

Here's my invoice contents.
2017.02 E39 M5
7430 GC 180.64.75: 7 inches long, 2 1/2 I.D., 430 lbs/inch 2
9280 GC 230.64.49: 9 inches long, 2 1/2 I.D., 280 lbs/inch 2
CCPE39M5 Camber/Caster Plate - E39 M5 (Pair)
bmwmountM5 Rear spring / shock mount, BMW e28, e21, e34, e39. 2 1/2 spring only 1
Strut MacPherson Strut Housing, part of kit requires strut inserts listed below. *RED 2
1547spgc Ground Control Custom valved Koni strut insert, top adjust 2
1225spgc Koni single adjustable shock, top adjustment, custom valving 2
bumpstop Ground Control Bump Stop 4
/QUOTE]


So I have a 380 rear spring and it's harsh when cold outside, so I think I'll have to go with a 300 instead, but does that also mean that I have to send my rear shocks out to get it adjusted to the new spring rate? Who did you deal with at GC?


Sent from AutoGuide.com Free App
 

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So I have a 380 rear spring and it's harsh when cold outside, so I think I'll have to go with a 300 instead, but does that also mean that I have to send my rear shocks out to get it adjusted to the new spring rate? Who did you deal with at GC?


Sent from AutoGuide.com Free App

You're saying that the mild fall temperatures are affecting the spring rate?
 

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You're saying that the mild fall temperatures are affecting the spring rate?
No sir, I never said that. What is happening is that the bushings get stiff from the cold and it makes the ride even more harsh. I just spoke to someone at GC and I was told to go with a 280lbs or 310lbs spring, so I am deciding on which one to go with.

Stock spring rate is around 300lbs at full compression ( progressive) the 280lbs liner spring would be 10% stiffer than stock. By going to 280lbs spring from my current 380lbs it would make the rear 26% softer and the 310lbs would be 18.4% softer.

The car is being tracked once in a while so which one do I go with?

Front Spring GC 180.64.75 - 7" long - 2 1/2ID, 430LBS
Rear Spring GC 200.64.67 - 8" long - 2 1/2ID, 380LBS

So what I am thinking is that I should take my rear spring and install it in the front and than get a 280LBS for the rear. Would that work, or keep the 430LBS at the front?

I ended up with a 10" spring at 300LBS

Now, should I keep the 430front or install my 380 rear to the front?
 

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Stefan, thanks for the informative post! I think these are leading the pack for me at the moment for when I am ready to buy new suspension.
 

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Looks like Ill be going with GC 230.64.55: 9 inches long, 2 1/2 I.D., 315 lbs/inch

I was also told they are so slightly progressive and will range from 280lb - 320lb.

I will report back with results, and I might switch to the 380lbs at the front.
 

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Discussion Starter #17
Stefan, thanks for the informative post! I think these are leading the pack for me at the moment for when I am ready to buy new suspension.
As far as I can tell, they're also the only offering that can confirm a square setup for you on 275s with a 5mm spacer. They place an indent in the strut tower, and the perch is low profile to accommodate this. Something else to think about.
 

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As far as I can tell, they're also the only offering that can confirm a square setup for you on 275s with a 5mm spacer. They place an indent in the strut tower, and the perch is low profile to accommodate this. Something else to think about.
With the proper red indented GC front struts, you don't need any spacer for 9.5/275 ET22 up front. With the traditional yellow Koni GC, just like regular Konis and stock struts, you need the age-old 3mm spacer.
 
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Discussion Starter #19 (Edited)
With the proper red indented GC front struts, you don't need any spacer for 9.5/275 ET22 up front. With the traditional yellow Koni GC, just like regular Konis and stock struts, you need the age-old 3mm spacer.
Thanks, I was getting my wires crossed.


Here's a clearer shot showing where I've got the ride height. This is about 2 turns off of the uppermost settings.

DSC_0384 by Stefan and Sarah Walter, on Flickr
 

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That ride height is perfect - good job!
 
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