Date: Wed, 15 Mar 2000 15:14:34 -0800
From: "Scott D Miller" <Smiller_at_bart.gov>
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:
- E30 325i Sports are 16mm shorter than HDs.
- E30 M3 Sports are 16mm shorter than HDs.
- 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
(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
(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
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
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.
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