Re: Replacing EDC shocks w/non-EDC system

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As everyone on the E31 owners e-mail list knows, I worship at the altar of stock and I drive the bombed-out streets of Washington, D.C. So when the EDC shocks on my 1991 850i finally got soft at 80,000 miles my first choice was to replace the EDC BMW shocks with non-EDC BMW shocks. In addition to using stock parts, my goal was to retain the original ride height with it's relatively forgiving suspension feel. In the rear, replacing the shocks is pretty straightforward because the they are separate from the springs. But in the front it's more complicated because the shocks are part of the McPherson struts. So at the outset, I identified four options:

(1) Install new BMW struts that use non-EDC BMW shocks.
(2) Rebuild original struts using BMW replacement shocks.
(3) Rebuild original struts using Bilstein replacement shocks.
(4) Obtain an "empty" BMW strut and rebuild it using Bilstein shocks.

Obviously, option 1 appealed to me from the start. But the complete struts list for $486 each and two new wheel hubs are required to bring my 1991 850i up to the 1992-forward configuration. (I can't recall exactly what they list for, but $169 each sticks in my mind.) Another problem was that the complete front struts were nowhere to be found in the BMWNA supply system.

My mechanic convinced me to at least consider a less expensive solution. (Believe it or not. What a great guy.) So I agreed to let him make some calls. In short order, we learned that option 2 was not feasible because BMW doesn't sell the front shocks as a separate part, and we learned that option 4 wouldn't work because BMW doesn't sell empty front struts for the E31.

That left option 3, rebuilding the original strut using Bilstein replacement shocks. My mechanic argued that this would create in a strut every bit as good as the non-EDC replacement struts from BMW, but using parts that we already have (or which are easily obtained) at a savings of about $280 per strut. I respect my mechanic's judgment, so I authorized him to investigate that option.

The first challenge with option 3 is rebuilding a strut that not really designed to be rebuilt. There is anecdotal evidence that a few people have managed to do this, and my mechanic thinks it *might* be possible. So I ask the group: Has anybody rebuilt the OEM front struts (whether EDC or not) replacing the OEM shocks with Bilstein shocks?

The second challenge with option 3 is getting the correct Bilstein shocks. Surfing over to: http://www.eshocks and examining the Bilstein application chart, I see that there is nothing listed for my 1991 850i. For the "92-96 840/850," however, the chart says that the MSP-05491 will work in the front and the MSP-05490 will fit in the rear. These shocks are listed as featuring the "sport" valving. So I ask the group: Why does Bilstein not offer a shock for the 1991 850i? Is it because the 1991 850i has the "old" wheel hubs? If so, will installing the "new" wheel hubs allow the Bilstein MSP-05491 shocks to be installed in the OEM strut? Does anyone have experience installing these particular shocks on a 1991 850i? Does anybody have a contact inside the Bilstein organization who can answer these rather technical questions?

The third challenge with option 3 is the compatibility of the Bilstein shocks with the OEM springs. Is it possible the springs on an EDC-equipped E31 are *different* from the springs on a car *without* EDC? In other words, is there any difference in spring rates? So I ask the group does anybody have any BMW reference documents containing the spring rate information we need to answer this question?

So as I write this on Friday afternoon, our plan is to start bright and early Monday morning with removing the front struts because no matter what we do they have to come out of the car. Once the struts come out, we'll see if they can be rebuilt with the Bilstein replacement shocks. In a perfect world, it will prove possible to rebuild the original struts using the Bilstein replacement shocks and our research will indicate the original springs can be re-used. If that's the case, we'll install the rear shocks, align the car and take it for a test drive.

If it turns out the original struts *cannot* be rebuilt, we'll fall back to option 1, installing new BMW struts already built up with BMW shocks. Fortunately, my mechanic had the foresight to order the BMW struts from Germany when we began this project over a week ago and they have recently arrived. So we have them if we need them. If we install the new BMW struts, we'll again have to ensure spring rate compatibility � this time between the front and rear. And we'll have to install matching BMW shocks in the rear vice the Bilsteins so that the shock valving will be identical all around.

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