The Sublime Suspension
The fourth and (allegedly) final pandemic project was refreshing the suspension. The car rode on what I believe was the original suspension: Alpina/Bilstein shocks, Alpina progressive rate springs, and adjustable Alpina sway bars. As far as I could tell—as I alluded in previous posts—the shocks were original both in that they were genuine Alpina/Bilsteins and they seemed to be the ones installed by the factory back in 1981. If right, that meant they were old, almost 40 years old, and the way they felt backed that up: they were worn out and bouncy. When at speed, the car felt like it was floating.
But I suspected the float wasn’t just because of worn out shocks: I thought that the progressive rate springs were also contributing to the problem. Designed to be supple on rough roads but capable of hard cornering, progressive rate springs are great in theory. In execution, however, they can be too much of a compromise, being subpar at both jobs. I don’t know if suspension preferences changed over the years or what, but I wanted to see if stiffer springs would produce a firmer, more satisfactory ride.
The final component are sway bars. Vintage Alpinas have sway bars that are a little thin compared to other performance sway bars, but they have five fixed adjustments, giving them the ability to feel pretty stiff if you use the extreme adjustment points. I saw no flaw with their design and, given that they can’t really wear out, I had no reason to think the sway bars weren’t doing their job correctly.
With this, my task was to get the Alpina shocks rebuilt and find some different springs. I took the shocks to a suspension shop at Sears Point—oops, I mean Infineon Raceway—that was recommended by a fellow Alpina nut. He had the shop rebuild the struts on his genuine Alpina 2002 race car and they did a great job. After they torn down my shocks, the shop called me with the bad news: the Alpina shocks were so old that they had thinner rods than current Bilsteins and parts for my older version were no longer available. I had three options: they could use new rods in the old housings, they could custom make the parts, or they could get new Bilsteins and re-valve them to Alpina spec. I went the latter route, which cost less than new rods in my housings or custom parts. Rebuilding the shocks was supposed to take 2 weeks but because they needed to order new Bilsteins, that delayed things.
While waiting for the shocks to be rebuilt, I searched for springs. I couldn’t find any from my usual vendors and discussion on the vintage BMW boards led me to believe that no one was manufacturing springs for the e12 bodies. So I looked for used springs on the various boards. The only ones I could find were an unknown brand but, having no other options, I scooped them up. Then a fellow BMW nut told me H&R springs were available for the e12 in Europe. I checked German eBay and sure enough they were. I ordered a set and will sell the unknown springs. It took time for the springs to arrive from across the pond, further delaying the suspension project.
The delayed project became a theme—on all the pandemic projects with this car, but especially for the suspension. The suspension was the start of the project (beginning in February of 2020) yet it kept getting delayed because I didn’t plan it well. I’d make a little progress but find that I forgot to order something, like a spring pad here or the special, beefy washers that go between the strut and the strut bearing there. I probably spent a month and half all tolled just waiting for parts.
The, after getting all the parts, my personal, non-car life took up all my time. A month later, things calmed and I was able to complete the reassembly and install the suspension.
As I reassembled the suspension, I had to make a decision on the rear suspension height. The rear Bilsteins have two slots (about three-quarters of an inch apart) and a clip that went into one of the slots to support the spring perch. I wasn’t sure which slot to use; I went with the higher one although I’m not sure why. It was just a guess. Below you can see the two slots with the clip in the lower one.
Installation was straight forward.
During the installation I got a closer look at the brakes. Many Alpinas have unique brake parts and the B7 is no exception. The calipers on this car appear stock (haven’t measured them, so I’m not sure). But the rotors were definitely not stock as they were slotted and had a big ALPINA name and part number on them. Everything on the rear appeared stock, though. Guess I’m going have to careful not to wear out the front rotors!
The wire holds the bolts at the bottom of the struts in place (in addition to a generous amount of Loctite).
Once back on the ground, I test drove the car to get it settled on the new suspension. After a bit of a drive, I got out to look at the ride-height and it seemed the rear was too high. My guess as to which slot to use seemed wrong; it seemed to be sitting a little high in the rear.
I went back and forth on whether to try the lower slot. Was it really too high? I looked at pictures of the car from the Bring-a-Trailer auction. In those it looked lower.
Finally, I acknowledged the obvious—that it certainly was lower before. So I decided to try the lower slot. But how to move to the clip? Did I have to remove the entire rear shock assemblies? I really wanted to avoid that.
I talked with a mechanic friend and he suggested loosening the nut holding the shock to the top strut mount attached to the body, lowering the shock and propping the spring perch up, giving me room to move the clip down to the lower slot. That sounded right but did I need three hands to do it? My wife, 30-some years ago, used to pump the brakes for me when I was bleeding the system. But asking her to get all dirty working under the car seemed like a fool’s errand. I wondered if there was a way to do it myself. I figured I could try loosened the top nut and propping up the spring perch with a 2x4 I had lying around. It worked like a charm. I had plenty of room to pry the clip out and shimmy it down to the lower slot.
With the clip on the lower slot, and a drive to settle the suspension, I got out and saw the car at the perfect height. Mission accomplished!
Ok, the suspension was in and at the right ride height. But how does it handle? Much better. The car is firmly planted at all speeds but still supple enough over bumps. I can’t say it handles as well as my daily driver—one of the best handling cars in I’ve ever driven, a mid-engined Porsche Cayman S. That car drives like it’s on rails. The B7 isn’t that good but it is one of the best handling 4-door sedan I’ve driven—especially for a vintage sedan. And I used to drive some pretty good handling sedans, including a e34 540i M-Sport with the Nurburgring EDC III electronically adjustable suspension. I used to call that car a 4-door 911 because it handled so well. The B7 handles better, partly because it’s a much lighter car, making it more tossable.
You’d think the completed the suspension refresh was a total success, but it begat a few new issues: the brakes pulled to the right on hard braking and there were some new, strange sounds. Finally, while under the car, I noticed grease splattered on the differential cooler and trailing arm. Upon inspection, I saw that the axle boot was torn.
Oh well, guess I have a few more pandemic projects now. Good thing we're not out of quarantine yet. Two steps forward, one step back….