The Spring Is The Thing

I’ve mentioned my good fortune to be living in the Colorado mountains, between the Continental Divide and the prairie abutting the Front Range, where many of the roads I travel are winding, steep, and lightly trafficked. In pre-pandemic, pre-lockdown times, when I was commuting daily, my budget for brakes and tires ran well above what it had been in the Pacific Northwest. I’m not complaining; paraphrasing George Best, “I spent a lot of my money on fast cars, brakes, and tires—the rest of it I squandered.”

However, with my sustained enjoyment of the twisty bits, other higher-order effects and wear patterns came to light. In the case of our E91 3 Series wagon, which has now over 80,000 miles, a looseness in lateral transitions—say, from a right sweeper to a left to a tight right—became un-ignorable.

Inspection of control-arm bushings, sway-bar links, and ball joints uncovered no failing components, but the dampening elements—the rear shock absorbers and front struts—seemed a tad squishy. I checked the maintenance records, which jiggered my memory to recall that they’d all been replaced after the car’s win at Targa Newfoundland. So the dampers and mounts had… less than 40,000 miles on them? A snide voice in the back of my mind carped about the car’s weight and the driver’s enthusiasm, and queried, “How exactly did you think BMW made it handle that well, anyway? Yes, it will consume some parts. Deal with it.”

Damn straight: If they’re tired, it’s nobody’s fault but mine. If they’re not tired, I’m just not drivin’ right.

Besides, there’s a simple remedy. I have a fondness for yellow-and-blue Bilsteins, and the B6 variety were easy to find online, so I ordered all four. Replacement springs—the factory-installed units were still on the car—proved a bit more difficult to locate, owing to the wide variety of spring rates fitted to the E9x cars: Each rate is targeted at a particular combination of chassis (coupe, sedan, convertible, sport wagon) and options. But eventually new coils, too, came to our hilltop domicile, so I set about replacing the boingers.

The toughest part of replacing the rear shocks was tearing apart the trunk-liner panels to reach the upper shock mounts. I judiciously used a nice floor jack to gently unload the swing arms on which the lower end of the rear coils press, and got the new rear springs in easily. On to the front!

Just last year I replaced a set of front springs on the 1990 325iX. Those iX springs are simple old-school “parallel coil” units (I’m not sure what the right technical term is):

Parallel-coil E30 front springs.

This style of spring can be compressed—with extreme caution—using a low-end set of spring compressors like these:

Garden-variety spring compressors: better than nothing?

But the coils for the front of the wagon aren’t parallel-coil; they’re more like spwatskity coil. Here’s a comparison photo:

E91 front coil spring next to E30 front coil spring.

Technology marches on. The E91 coils, despite weighing less than the E30 coils, have to contend with much more car weight. I suspect (not having taken any higher-level physics courses) that part of the force-rating on the E91 coils comes from their skewed resting state. That’s a guess, mind you, but compare the springs in the picture above and know that the left spring has the “heavier” rate. I regret that I am unable to describe with any authority why this should be so.

I can say with high confidence that trying to use the garden-variety spring compressors with those spanguladar springs is a dumb idea. It’s not the right tool—not even close. I’ve got a healthy respect (read: fear) of high-powered springs, so when I was attempting to compress the new E91 coils, I had on all my PPE and as much shielding as I could interpose between my weak flesh and those hellish steel windings. Two careful efforts misfired, and while I’m often stubborn and impatient, my imagination painted horrendous accidents so easily that I decided that I lacked the required expertise necessary for assembling the struts.

Having reached the safe limits of my skills (and my tools), I ceased my efforts and considered finding help.

As detailed in an earlier column, the repair shop nearest to me wasn’t an option. Down the mountain, an hour away, is a great BMW dealership; at the same distance, there’s a clean and competent independent BMW shop; and a bit closer is the franchisee of a major tire-store chain whose mechanics have so far produced decent work. But hey: An hour one way is two hours two ways—as rallyists say, “For every mile of road, there’s two miles of ditches!”—not counting the actual execution time for the wrenching.

Then I recalled a blurb in the local rag describing a new shop, specializing in European makes and in bespoke electric conversions for classic cars. Their calling card has a silhouette of an E30 nose—always a good sign—and their Facebook reports of a current electro-conversion project (a dual-motor Tesla power unit into a Land Rover) piqued my interest. So I threw the struts and the curvalicious springs into the back of the X5 and drove up to Rollinsville, Colorado to visit the place.

I arrived just after opening time on a Monday morning. I believe that this time is reserved in most auto shops for finishing up what didn’t get done at the close of the previous week; it’s a paperwork storm, with side flurries of calls to suppliers and customers—busy, in other words. But Woodson, the owner of ElectroMod Garage, popped out quickly to see what I needed.

What I needed was the right tool, and the expertise to use it. He had the tool, and facing the crush of start-of-week work, he accepted my waiver and allowed as he’d let me use it outside the shop. I was flattered that I had given him the impression that I might know what I’m doing.

Even with a strut clamped into the professional tool, however, the arched spring presented challenges that had me tentative and slow. After a bit, detecting my ineptitude, Woodson cheerfully took over, with me assisting.

I take a tiny bit of comfort from the fact that, even with his expertise applied to the problem, we still hit some snags. I was also completely convinced that I’d made the right choice when I stopped trying my low-end approach. Pretty quickly we had a very pretty pair of assembled struts.

A safe and speedy tool for strut work (and a Tesla power unit awaiting installation in a conversion).

It might have gone faster if we’d not paused to look at the M60/M62-swapped 325iS outside, and examine the mounts for the Tesla-to-Land Rover transplant. To tell the truth, I could have spent more time there—but we both had to get back to work.