Problem: Can’t find springs with the correct ride height for you, want to run stiffer springs than normal?
Solution: Ground Control Coilovers
Overview:
E28’s already have a coilover style suspensions setup; however, it is not adjustable in ride height and there are a limit as to what spring rate you want to run. Ground Control sells a kit for e24/e28 chassis cars, however, this is not a bolt on product like the typical spring and shock upgrade. Cutting, welding, and sum fabrication is required to properly fit the front coilovers on the strut.
Also, Ground Control recomends running Koni's with their setup because stock Bilstein Sports cannot handle the higher spring rates; however, it is still possible to run Billie Sports, you'll just have to get them revalved for that higher spring rate. And with Bilsteins or Koni's you'll want to run a 7" or 8" free length spring in the front and a 8" spring in the rear to have maximum adjustability (from stock height to 2" lower).
A good starting point for this setup, spring wise is 400lbs/in front and 300lbs/in rear with either a 7" or 8" spring in front and an 8" spring in the rear.
Some more info on shock choices courtesy of Peter Florence:
Items Needed:FirstFives Dictator wrote:Koni 8610-1437Race inserts from TrueChoice. I think GC can supplied them valved for your car and spring.
Another note: the 8610 are 1/2 turn off full stiff when I autocross on old AS04 tires. So ordering them with custom valving may be the trick.
Be sure to read the instructions and be ready to make a spacer to go in the bottom of the strut. For me it was about 3.5" pipe from my old chainlink fence. I think on E28 it will be a little longer. The 8610's come in 2 lengths; get the longer one. It has more travel.
Details here on spacer:
http://www.firstfives.org/wb/msgs/32815.html
Tool wise; you will need a grinder/ cut off wheel, MIG welder, and other basic tools to disassemble your front and rear suspension. FOR SAFETY, if you do not have a spring compressor to remove your old springs, I highly suggest you rent one rather than doing the lock and chain method.
You will need to call Ground Control directly or order through a local distributor to get the best setup for your needs. Some have had bad experiences with Ground Control customer service; however, I have no complaints. I would also like to note, that while ordering the coilovers, mention that you want 7" or 8” for the front as the 6” springs they send you are incredibly short for our cars unless you are track dedicated and don’t plan on driving over any bump that will destroy your oil pan, ask me how I know! Tell GC or whoever you are ordering through the intended use for the car and they will give you their opinion the ideal setup for your specific needs.
I cannot tell you exactly what to order since this setup is very customizable; however, I can give you my items ordered and I’m sure others who have purchased and installed their product can chime in with their setups so we can have a nice collection of GC setups for people to reference.
It is recommended that when using spring rates of 450lbs/in and above that you use a strut brace to avoid cracking of the shock tower; however, I’ve never seen such a thing and there are people running much higher spring rates than I. I went ahead and opted for front and rear Ireland Engineering strut braces, be aware that some front strut braces have limited room for adjusting the camber plates if you decide to run them so you may want to check the clearance to see if you’ll be able to adjust camber without removing your strut brace every time, my IE bar has enough room for full adjustability.
Step One: Removing the Front Strut Assembly
As usual with any suspension work, get the tires off and put her in the air, make sure that the car is secure. To remove the front struts, you’ll have to take off the caliper, brake disk, ABS sensor, sway bar, bottom strut assembly, and strut mount. Begin by removing the caliper, then the brake disk. Then remove the ABS sensor by loosening the fastening bolt (I believe it is a 5mm allen ) and then popping it out with a flat head screw driver, it will be pretty hard to remove but it’ll come out. By removing the ABS sensor, you have now disabled the ABS, and the sensors are designed so that when they are removed, they break; therefore, you’ll have to order new ABS sensors if you want your ABS brake system to work. Now that you’ve got the caliper and disk out of the way, unbolt the sway bar, secure the spring with a spring compressor, and unbolt the 3 bolts for the strut mount at the top of the strut. Once all of that is done, there are 3 17mm bolts that hold the bottom strut assembly on, unbolt those and finally, remove your strut assembly. Now, you can unbolt the strut bearing from the chassis, there are three bolts, it a bit tight up there in the shock tower but is very do-able. Now that all of that is done, you should be able to pull the whole strut assembly out (strut bearing, spring, shock, strut housing, bearing, and dust guard).
Now that the strut assembly is out of the car, the next step disassembling the strut assembly.
Step Two: Disassembling the Strut Assembly
Now is the most dangerous part of this disassembly, car springs have massive amounts of energy stored in them and you must perform EXTREME CAUTION when taking the strut bearing off and removing the spring. First you’ll need to get a spring compressor (you don’t have to buy one, you can easily rent one from your local auto parts store), now after compressing the spring so that there is little to now force being applied on the strut bearing. Once the spring compressor is set correctly and firmly tightened down, it should be safe to unbolt the top strut bearing. I believe it is a 19mm bolt and you’ll most likely need an impact gun to get it off, it is do-able, but once again very hard and remember to be careful that the spring is securely fastened and tightened down in the spring compressor, I can’t stress this enough. Once all of that is done, you’ll need to remove your shock. There is a collar nut on top of the strut, I removed via a chisel and a hammer and it worked great. Now that you’re shock, spring, and strut bearing are removed from the strut housing, it is time to start modifying the strut for the coilovers.
Step Three: Modifying the Strut
Here are were pictures come in handy, when I did this project I used this site as a reference. Here is what my strut looked like after modification:
Notice that the spring perch that held the stock setup spring is gone and there is a new, much smaller perch welded in its place. That is essentially what you’ll have to do. I started by using a hacksaw to remove the majority of the metal from the spring perch, then I grinded the rest down. Make sure to measure from the top of the strut mount to where the old bottom of the spring perch was, this will be where your new spring perch will be welded. Or you could grind down the old spring perch just enough to leave a little lip left on the strut and this can be your new marker for the spring perch, either way is acceptable, I measured and grinded mine all the way off but I know some people used the latter method. This is also a good change to reinforce your sway bar links just incase you ever plan on upgrading, there are pictures in the link above on how to reinforce your mounts. Also make sure you do all your welding and grinding with the shock out, if it gets hot enough it could explode and that would not be good at all! Now that you’ve modified the strut, it is time to reinstall the strut assembly.
Step Four: Reinstalling the Strut assembly with Coilover
It can be a bit confusing will all this shinny new hardware going onto your suspension and because this setup is a little different than stock, the order of assembly may be a bit confusing.
Here is what the finished strut assembly will look like:
http://picasaweb.google.com/tigrfan/200 ... 5930710546
First you’ll need to put the new strut in, along with the adapter spacer if you have Koni’s, and tighten the collar nut. Then you can put the actual coilover sleeve in (the red threads and gold adjustable perch). After that, put the dust guard on, and the bump stop. If you get adjustable camber plates like I did and the pictures in the link above has, it will be installed exactly like a strut bearing since that is essentially what it is, it just has a large stack height and is adjustable for camber and caster. Put the camber plate or strut bearing on the shock and make sure to use a little installation grease as it is a bearing and it can be a little tight sometimes but it will go on easily. You can either torque down the top bolt off the car or on the car, on the car it is easier but either way is do-able. Now just refer to Step One but do it in reverse for the installation, make sure to tighten everything according to the torque specs.
Now that you’ve installed the front, it is time to drop the car onto the wheels and adjust the height accordingly to what you want. Also, if you’ve installed Koni Single Adjustable Shocks, you can only adjust rebound. I drove around a couple of time and adjusted the shocks accordingly to where I liked them. I haven’t touched my shocks since I installed them, but if I recall correctly, you’ll need to loosen the top strut bearing bolt every time you adjust them. Also, if you’ve installed camber plates, I’m running a -1 degree camber for my everyday driving and I don’t notice any weird tread wear, and I adjust them to -2.5 when I auto-x or go for very spirited drives on those early Sunday mornings
!Time for the rears!
Step Five: Rear disassembly and Installation
The rear disassembly and installation is much easier than the front and requires no modification. Again, you’ll need to used a spring compressor to compress the springs for removal; remember to exercise EXTRME CAUTION as there is a lot of energy stored in the springs. After you’ve safely secured the spring, you can start unbolting the rear shock from the trailing arm and from the shock tower. After all the bolts have been removed, you should be able to remove the spring and shock; before that though, again, make sure that the spring is securely fastened in the spring compressor and there is no tension on any perches.
After everything is removed you can put the coil over setup on the shock. Remember that Ground Control suggests running certain shocks for a proper setup, I bought Koni’s directly from them and that is what they recommend but people do run Bilsteins, but if you have a high spring rate you may need to get them custom valved, just be aware and consult a Ground Control customer service representative to talk about what you plan on doing with the car.
Here is what the rear setup will look like once everything is assembled:
I just noticed that I didn’t have the shock mount installed in this picture but you’ll need to install that on top of the spring along with the spring pad they supply you with. Also refer to the link in Step Three for pictures of what the rear assembly will look like. Once you have the rear assembly put together, you can now bolt it back up to the rear trailing arm and shock tower.
Now that you have the rear all bolted down to specs, you can now lower the car back onto the wheels and choose the appropriate height you want.
Step Six: Enjoy the Hell Out of Your New Suspension!
Remember, if you find that you’re springs are too short or you think they maybe a little to stiff for your liking, you can contact Ground Control for new ones. They replaced my front springs which were obviously too short like a warrantee but new springs are $150 for a set, any rate, any free length spring you want.
I hope this helps get a good FAQ started for GC install. Personally, this mod is the best thing I’ve done to the car and I don’t regret doing it at all, the adjustability and customizability of this setup really impresses me, not to mention the sheer performance. When I had my 27mm 4-way Adjustable front sway bar on (which I have removed for now due to cracked mounts) and my rear M5 bar, the car was flat out in every turn and would change direction with amazing sharpness, if you’re local (San Diego) and are contemplating this setup, let me know and I’ll gladly give you a ride.
Also, as a little bonus to the FAQ, I thought it might be a good idea to get a collection of info on what people are running so that people contemplating this can see what people run and ask them about their custom setup:
I’ll start.
DaRedRocket:
Shocks-Front: Koni Single Adjustables
Shocks-Rear: Koni Sports (Yellow Ones)
Springs-Front: 440 lbs/in, 7” free length
Springs-Rear: 300 lbs/in, 9” free length
and
Springs Front: 650lbs/in 7" free length
Springs Rear: 750lbs/in 6" free length
Bimmerguy2002:
Shocks All Around- Revalved Billie Sports
Springs-Front 520lbs/in, 7" free length
Springs-Rear: 750lbs/in, 8" free length
Note: Having a higher spring rate in front is not recomended as it will not keep the stock proportionality of spring rates the cars were designed with, a higher rear spring rate will tends toward oversteer and a higher front spring rate will tend towards understeer.
If people could follow this format for their info on their setup, that would be awesome!
References
Paul Peters
Also, here is a stock list of all the springs options that GC supplies:
http://www.ground-control-store.com/pro ... .php/CA=31
And here is what the GC setup comes with/ minus shocks or camber plates:
http://www.ground-control-store.com/pro ... 674/CA=102
Here are the Adjustable Camber Plates:
http://www.ground-control-store.com/pro ... =689/CA=68
Here are the optional rear Billet Alluminum Shock Mounts:
http://www.ground-control-store.com/pro ... =675/CA=68
Enjoy.