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Ground Control Suspension
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A few important details


Front strut housing after welding on collar and sway bar mount reinforcement To convert your factory struts for use with the Ground Control front adjustable threaded spring perch it is necessary to cut off the existing factory perch and grind it down. Then you weld on a steel collar provided with the kit. The threaded barrel sits on top of this collar. Since I was cutting and welding the strut housings I decided it would be a good time to add some reinforcement to the front anti-roll bar mounts. These are known to crack on E30 M3's especially when using uprated anti-roll bars.

I purchased the ready made reinforcement plates from Turner Motorsport. The reinforcements are nothing fancy, but it would take some time to reproduce them. Since they are fairly cheap I decided to go with the TMS units. I used a bolt to hold them in place during the trip to the welder's. If you do not feel comfortable modifying your own strut housings, then you can send them to Ground Control to have it done. Based on my experience this may not be a bad idea. The welder who did the work on my strut housings used too much heat. This caused the beads to penetrate through the housing quite a bit. So when I went to insert my Koni strut cartridges into the housings you can guess what happened. No go. The fit between the cartridge and the housing is very tight. It took me the better part of a day with a Dremel and a file to get the housings in. Not fun.

After painting the strut housings look better than new. And without the ugly factory spring perch!


Front strut housing after painting

To those of you who are interested, I used the following settings for the Koni SA dampers:

Fronts @ full stiff minus 5/8 turn
Rears @ full stiff minus 1/4 turn

Since there are roughly two full turns of adjustment available, these settings are on the stiff side. But the 450 lbs/in front and 575 lbs/in rear springs are also quite stiff, so Jay recommended settings that would be appropriate. During my first outing with this setup at Laguna Seca the current settings proved to be very good. I cannot yet see any reason to alter them. Click here for a look at the shock dyno charts for the Koni Single Adjustable dampers

I obtained the GC springs and perches through a trade. That determined my spring rates. If I had been able to choose my own rates I probably would have gone with 400 lbs/in front and 600 lbs/in rear (I am still using the factory sway bars). But now that I have driven with the 450 lbs/in front springs I see that they are not too stiff for street duty. So I may eventually go with stiffer rear springs - say 650 lbs/in. This should shift the balance of the car a bit more towards neutral. As it is the car is probably biased more towards understeer then it should be for optimum handling. But is nonetheless very tossable and incredibly flat.


Rubbing problem with retaining collar

One last thing. The photo at left shows what happens if you use the 2.5" ID racing springs with the factory E30 M3 strut cartridge retaining collars. The collar is so wide that it WILL rub on the spring producing a horrible squeak (problem area is indicated by the blue arrow). The fix is to use the Koni retaining collars, which are smaller in diameter and give the spring plenty of room to move up and down (shown on the right). Unfortunately, the E30 M3 Koni SA's do not come with these collars so you have to make sure and order them separately. Do not get lazy like I did and assume that it won't be a problem. Or else you will spend another perfectly good day taking the whole front end apart in order to swap the collars 8^(



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Home
Back to Installs
place holder
place holder
Installs Part-1
Installs Part-2
Installs Part-3
Ground Control Suspension
2.5 L Engine Rebuild
M Coupe Diff Cover
Custom Ergonomics
Sparco Stress Bar