As I am sure most of you recall, my 1991 850iA was fitted with Electronic Damping Control (EDC) shocks at the factory. And as I'm sure you recall, after about 80,000 miles the EDC shocks were getting quite soft and it was time to replace them. Your Faithful Moderator worships at the altar of stock, so my first choice was to replace the worn EDC shocks with new BMW parts. The problem with that idea was that new front struts equipped with EDC shocks were a whopping $1,040 each and new EDC shocks for the rear listed for an equally expensive $820 each. Even by E31 standards, that's outrageously expensive.
As I have more fully described in previous posts, my mechanic talked me into relaxing my rule against aftermarket parts so that we could investigate using Bilstein Sport shocks. As many of you know, it is possible to rebuild the front struts using Bilsteins, and the rear shocks bolt in easily as well. But the Bilstein Sports are about one inch shorter than the BMW shocks they replace. But I was not interested in lowering the car or installing aftermarket springs. So it was back to the BMW parts bin.
In a perfect world, BMW would sell separately a non-EDC shock that you could use to rebuild the front struts on a car that was originally equipped with EDC. It would be the same shock (also known as an "insert") that is installed into the front struts on E31s that were not fitted with EDC. But BMW refuses to sell that shock separately. So instead of purchasing a front shock/insert for, roughly, $150 you have to pay a $486 for the entire strut assembly. Granted, the $672 difference for the pair isn't going to bankrupt anybody. But it's annoying to be forced to spend money unnecessarily. I can't imagine that there is anything too exotic about the front shocks/inserts on an E31. So I would think that if we could figure out the dimensions and specifications, it would be a simple matter to obtain a replacement from Boge/Sachs. As the E31 fleet ages and BMW parts become more scarce, I predict this approach will become standard for those owners who don't want to install the shorter Bilstein Sports.
As Mr. Castle noted in an earlier post, the BMW parts CD shows three different replacement struts are available for an 850i with a June of 1991 build date. (Note dual part numbers for left and right struts.)
Sporty / Tropical 31 31 1138 551/552
Comfort 31 31 1138 553/554
M Sports 31 31 1139 653/654
I don't know for sure how these three struts differ. Based *solely* on an examination of the parts numbers, I theorize that both the "sporty/tropical" and the "comfort" struts result in the same ride height, as indicated by the "1138" portion of the number. I further theorize that the shocks are valved differently, with the "sporty/tropical" valving being somewhat stiffer than the "comfort" valving. (Duh!) Finally, I theorize that the "M sports" struts are fitted with a physically shorter and stiffer shock (similar to the effect obtained by installing Bilstein Sports) and thus a lower ride height is obtained. The "M sports" struts probably require use of shorter and stiffer springs as well. But note well: This is pure conjecture on my part. If anybody has any hard technical data on how these three struts differ, please send it along.
I drive the bombed-out streets of Washington, D.C. on a daily basis so I opted for the "Comfort" struts. As noted above, they were $486 each. Yes, I know that's list price. And yes, I know that I can purchase BMW prices for less than list. But I want my mechanic to make a living. So I cheerfully pay list price for parts, knowing he pays less than list and it's part of his profit margin. I'm sure he could juggle the figures such that I received a "discount" on parts, offset by a corresponding increase in his labor costs, resulting in the same total charge. My point is that my car is fastidiously maintained by a excellent independent shop where I deal exclusively with the owner - a mechanic who patiently tackles weird E31 projects like this one. So I pay what he charges.
The following additional parts were also necessary to complete the job:
Rear shock 33 52 1137 479 Two at 132.00
Wheel hub, front 31 32 1468 926 Two at 121.60
Absorber 31 33 1124 449 Two at 14.90
Absorber 33 53 1134 043 Two at 26.25
Guide support 33 52 1091 605 Two at 23.00
Washer 33 52 1134 028 Two at 0.77
Tube 33 52 1134 044 Two at 3.25
D nut 31 21 1128 336 Two at 6.20
Cap 31 21 1130 124 Two at 3.25
Dust collar 31 21 1136 466 Two at 1.79
According to my mechanic, the BMW parts gurus absolutely insisted that new ABS sensors were necessary. But when he tried to install the new sensors, the connectors were wrong. So he retained the original ABS sensors.
Installation of these parts is straightforward. The EDC circuitry was disabled by removing the relay in the trunk. The only unforeseen thing encountered during the job were tiny cracks in the front backing plates. In the case of my car, the cracks were so minor that we elected to weld them. If you do this job, be sure to inspect this part.
My mechanic charged $336 in labor to replace the front struts, replace the wheel bearings and to replace the absorbers. He also charged $280 in labor to replace the rear shocks, to replace the upper shocks mounts and to replace the dust cover and absorber unit.
The invoice does not reflect how many hours this took, nor does it reflect how much my mechanic charges for an hour of labor. But given all the research that went into this project over the past few months, given the fact that my mechanic had never replaced the shocks on an E31 (far less substituted regular shocks for EDC shocks) and given the care with which the job was accomplished, I think that $616 in labor was more than fair.
Finally, there was a $115 sublet charge for a full alignment. Adding $18 for "shop supplies" plus tax the grand total was $2,461.54. To be sure, this was not an inexpensive repair. But I have the satisfaction of knowing it was done carefully and with all BMW parts. Moreover, the original shocks lasted nine years so I'm confident these shocks will be similarly durable.
DRIVING IMPRESSIONS: When I opted for the "comfort" struts with matching shocks, I was concerned that the ride would be too soft. I need not have worried. The ride is firm without being harsh. More importantly, my suspension has all of the original travel remaining. (And I'm still running the original 50 series tires.) So when I do hit a pothole the suspension soaks up the insult with ease and there is absolutely no steering feedback. Speaking of steering, it feels somewhat quicker and more precise at slower speeds. (Also due, in part, to a recent flush of the hydraulic system and the installation of new CHF and a new filter.) As you all know, the E31 will never be confused with the file://M3 when it comes of darting around town. But my car feels far more nimble than it did when the shocks were soft and the hydraulic system was dirty and somewhat clogged. There is still a slight deadband when the wheel is centered, but it's not objectionable.
Out on the freeway at speed, the new shocks make a BIG difference. My car no longer floats over expansion joints and there is zero body roll when I take those decreasing radius off ramps at double the posted speed. And the suspension easily handles washboard pavement. In fact, when it comes to lateral acceleration I run out of guts long before my car runs out of grip. At speeds greater than, say, 75 mph the steering lightens up noticeably and my car has the superbly composed feel that it did when I bought it. Even lane changes that are initiated with purposely ham-fisted steering are utterly lacking in drama. The ABS works fine and there are no faults on the MID caused by the absence of EDC.
All in all, I'm happy with the results. As always, you may prefer a different suspension feel. But if you want to maintain an all-BMW setup that's comfortably firm without being harsh I can highly recommend the "comfort" struts with the matching shocks.
PMB
