We used Powerflex upper shock mounts on our rear dampers. Stock upper mounts have a tendency—on all these BMW 3 Series cars—to rip out when you combine stiffer springs rates and high-performance dampers with aggressive driving.
As we said in our first installment, our end goal on this project is to take on and beat a stock E30 M3 at the track all the while still maintaining a comfortable ride and staying within a reasonable budget. To meet our somewhat lofty goal, we would need to do some suspension modification without getting too wild in both our spending and specifications.
Stock E30s handle exceptionally well, but nowhere near as good as the M3. To this end, we installed an Eibach Pro-Plus kit, #2003.880. We have used their suspension kits on many project cars, and for street and light track use, have found them to be very economical (the kit retails for about $500.) This kit is more than adequate for improving handling without destroying ride quality.
So, what comes with the kit? We’re glad you asked: front and rear springs are included, as well as the corresponding anti-roll bars. The Pro-Plus kit lowers the car between one and two inches, reduces body roll and brake dive, and generally firms the car up nicely. It does this all without any of the adverse effects that a lot of suspension kits have. Installation of the kit was straightforward, and we encountered no squeaks, rattles or interference problems.
To complement our new springs and anti-roll bars, we needed to install dampers that would further us on our path to E30 M3 domination. Naturally, we turned to Koni.
We have been using Koni dampers for forty years on our project cars. Starting with a `66 Shelby back in `79, we discovered the combination of ride and handling that these Dutch made dampers offer enthusiasts.
As an added plus, Koni also works in concert with Eibach and makes the dampers that are perfectly matched to the Eibach suspension kit are using. The Koni Sport cartridges for the front up front along with rear damper are available at The Tire Rack or from Koni directly for about the same price, about $170 for each front and $110 or so for each rear damper.
In addition to the quality of these dampers and the compatibility with our Eibach Pro-plus suspension kit, the Koni Sport line offers external adjustability and a life time warranty. This adjustability can be used to fine tune handling at the track, or to soften the dampers for improved ride quality. Just what we are looking for.
Installation of the Koni dampers is as straightforward as the Eibach kit. The front inserts just slide into the strut housing. We do recommend adding a little lightweight oil to the housing to improve cooling, though. The front suspension of a BMW E30 is a strut design, so to make things quick and easy, we borrowed a friend’s professional, wall mounted spring compressor to mount the front struts, springs and camber plates.
Compress the springs, install the top hat (or in our case camber plates) and tighten the nut on the shaft. We topped our strut assembly off with Ground Control adjustable camber plates, which we will get into in a separate installment in this story.
At the rear, the dampers are installed after the subframe is back in the car, which we cover in the next installment. The rear trunk interior panels will need to be removed to bolt the top of the damper into the mount. As we mentioned in an earlier installment, we used a rear damper mount from Powerflex, as the stock ones can easily rip out of the body when using heavier shocks combined with aggressive driving.
To install the rear dampers, you mount the top of the damper to the body and then compress each corner of the rear suspension with a transmission jack (if your car is on a lift) or floor jack and slide the bottom of the damper into the mount on the trailing arm, and then tighten everything down.
After finishing up the installation on all four corners, we set our Konis on the middle setting, which we generally do to establish a baseline. We’ll fine tune them when we get to the track or autocross course.
One final note on suspension installation for one of these cars: the rear anti roll bar mounts are flimsy at best and will rip out with track or autocross use. Fortunately, Bimmerworld has a rear anti-roll bar mounting kit that goes all the way through the trunk floor, thus eliminating this problem completely. We highly recommend it.
Next time, we'll discuss the installation of the Ground Control camber plates.
Those Eibach springs are pretty soft, as in close to stock, are they not? Why not go with a stiffer spring and less roll bar? Interested to see what setting you wind up with on the Konis, I run those same shocks with a 450/650 spring setup on my DD, at close to stock ride height. Low is highly overrated on a street driven car.
Low is very overrated with the M42's low slung oil pan. Maybe look into a skid plate? Have anecdotally seen many a M42 destroyed on the internet by potholes and cracks in oil pans.
We just ran the car at full course at VIR and turned a 2:24. Other than the car being a bit loose at the rear, which we can easily fix, we are very happy with the way the car turned out.
Our intention is to drive it every day and while our roads are smooth here, and the car is quite comfortable on the street, I would not want it to ride any rougher, for daily use. Other than playing around with rear bar and shock settings, I think we have this baby right where we want her.
In reply to Tim Suddard :
The variety in suspension setups people run on street driven E30s shows how subjective comfort is. I find my firmly sprung and well damped E30 with solid UHMW bushings perfectly comfortable for a drive across the state, someone else may find it unbearably stiff. Roads are pretty good where I live, I do notice the occasional poor leveling and paving job because my car follows the road surface more than softly sprung stock cars do, but feeling variations in road surface is more tolerable to me than the underdamped ride of my Wife's '18 Corolla or the wallowy mess that was a recently rented brand new Jeep Compass.
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