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Date: Wed, 15 Mar 2000 15:14:34 -0800
From: "Scott D Miller" <>
Subject: [uuc] <E30 > Bilstein Shocks, Suspension Questions

Eric Ingraham and I have been having a running discussion (is it still a "discussion" when it is e-mail?) about Bilstein shocks/struts for E30s. The issue, to summarize from an earlier post, was whether the M3 and non-M3 E30s use the same, or different, shocks and struts. I was misled by the BMP catalog, which lists the same stock numbers for both cars. Eric contacted Bilstein (doh!, why didn't I think of that?) and came up with the answer, for which I thanked him profusely and offered him beer, assuming, of course, that he is of legal drinking age. OK, here goes:


Here's the final word:

  1. E30 325i Sports are 16mm shorter than HDs.
  2. E30 M3 Sports are 16mm shorter than HDs.
  3. Rear shocks are the same for each car, HD or Sport.

(B36-2028 HD, B36-2027 Sport)

4) Early E30s had a 45mm O.D. strut housing, and use smaller shock inserts.

(P30-0128 HD, P30-0334 Sport)

5) 325i's, 325is's, and M3's use a 51mm O.D. strut housing, and can accept a larger shock insert. However, the earlier (smaller) strut insert will also work.

(P36-0136 HD, P36-0335 Sport)

BTW, the first two numerical digits of the part number have something to do with the shock/rod diameter. Not sure if they are it exactly though (in mm).

That all make sense? The real sticking point is that the later cars *can* accept the earlier strut insert, which is what mail order places usually will sell you. However, the later, larger shock is the one you really want. Conversely, the earlier cars can only accept the smaller shocks (P30s).

If you press the boot in on the early vs. later shocks, you can really feel the difference in shaft diameter. I did this between the first set I got and the second set. Big difference.

Now, as far as ride height goes, I think this proves that it is only preferable, but NOT critical, that you use Sports for lowered springs. Next question (in order to beat this discussion into the ground) is how the stock M3 ride height compares to the stock 325i ride height. Since there are way too many variables to determine a statistically valid answer, I would say that perhaps shock rod length is a guideline at best.



So apparently I could get away with keeping my HDs and installing the M3 springs, which some Digestors said they have done and like. While this would keep the cost down, my preference would be to get the Sports, which will push back my target installation date while I come up with the cash. Then there is the matter of front camber. Keep my offset upper strut bearings? Get adjustable camber plates? (More $$$ here again.) If I knew lowering with M3 springs would push camber past neg 2 degrees, I'd reverse the offset upper bearings to get back to my target, which is between 1.5 and 2 degrees negative.

This would not be so complicated if I wanted to experiment. But I only want to do this once. Oh well.

And then Steve, the same guy that "sold" me the springs, offered me his old M3 sway bars, too, for a rediculous price. Now, everyone says the front attachment point is different for an M3 than on a plain 325i, but Steve thinks the bars are pretty much the same shape, and that the difference is in the end links. Anyone know for sure?

Now all I need to do is get the rest of my parts (spring perch pads?, what else?) and schedule an installation date. This should be fun.

Scott Miller
GGC BMW CCA #44977
1990 325i/isH

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