From digest.v7.n1275 Tue Mar 10 15:56:34 1998
From: Pete Read <read_at_arl.bna.boeing.com>
Date: Tue, 10 Mar 1998 08:00:23 -0500
Subject: Re: <E28> Bilstein HD vs 535is Bilstein Mtechnik

Pete Lehman asks:
>Does anybody out there know if there is any difference between after
>market Bilstein heavy duty shocks and the Bilsteins that came standard
>on the 535is?

Yes, they are somewhat different, but almost everyone buys the aftermarket Bilstein HDs (~$100 each) because of the "shocking" price of the original Mtechnik Bilsteins (~$200-$300 each).

(1/97 price book)
shock absorber front, Mtechnik (535is) 31 32 2 225 662 $198.74 shock absorber rear, Mtechnik (535is) 33 52 2 225 666 $313.35

Phil Marx mentioned the unusual Bilstein Mtechnik shocks a while back. My first thought was that Bilsteins are all the same, but I always pay attention to Phil's posts. I was interested enough to call Bilstein Tech Rep Cleve Hardaker. Here's what I found.

The 535is uses the Bilstein Mtechnik shock which was specially built for BMW with damping somewhere between the Comfort and HD shocks. Actually the design is normal Bilstein monotube except for a hydraulic/spring rebound stop above the piston to prevent topping out (it still has a normal compression bump stop).

Apparently the spring rate of the 535is was increased for more control, but BMW still wanted relatively light damping for a plush ride. This caused a topping out problem which could damage the struts.

To prevent damage, Bilstein added the extra rebound stop. However, during installation, this prevents the strut shaft from extending fully without some help. There is a special BMW tool to pull the shaft up during assembly.

Pete Read
'88 M5
Arlington, VA