The upper control arm bushings are a notorious shortcoming of E24 and E28 cars. These bushings take most of the load in the front end under braking and will cause the car to shimmy if worn. Some reputable tuners will sell you a pair of "heavy duty hard rubber" bushings for upwards of $250 a pair.
These bushings are nothing more than E32 750 bushings machined down to the proper width so they fit into the stock mounts. Save yourself a few bucks and order the machined bushings from The Ultimate Garage. They will also sell you new control arms with the machined bushings already pressed in. The ball joints in the control arms don't last forever so do yourself a favor and save yourself from doing the job twice. Get new control arms because you probably need them. You can see me removing and installing bushings on the poly bushing page.
You can save yourself a little more money by buying the 750 bushings and machining them yourself. The center metal portion has to machined accurately and evenly so a Bridgeport or similar milling machine is needed. The outer metal shell just needs to be trimmed back so that it won't hit the control arm mounts.
I lost the scrap of paper with my measurements but this post from the Big Coupe Grouppe sounds right:
Message Number: 20
Date: Mon, 10 Jan 2000 19:23:27 -0500
From: Robert Shelor <firstname.lastname@example.org>
Subject: 7 Bushings ... again
Ok, I now read the shell of a 7 series needs
to be faced down so as not
to contact the subframe. Steve Haygood was good enough to make me a real
deal on arms and 7 bushings. I got out my vernier calipers and did some
measuring. Here is the actual lowdown on sizes:
The shell diameters are identical at 58mm.
The shell length however are 47.5mm for the 7, and 37 for the 6 bushing.
The spindle length is 56mm long on a 7, and 50mm on the 6 bushing.
Knowing these measurements, I am assuming that
the spindle needs to be
faced about 3mm per side, but the shell length cannot be turned down 5mm
per side due to critical rubber bushing material being lost. My question
then is, how much is required to be removed on the shell? Steve
D'Gerolamo says to turn the shell down because it will contact the
subframe, but he doesn't say by how much. I'm too lazy and I also
injured my shoulder recently, or I would crawl under there and attempt
to figure it out myself . I plan to turn the things down, punch out the
old and in with the new bushing soon, and I don't want to screw things
up. So how much is enough?
I took the shell down a little less than 1/8" (~3mm) on each side and had no rubbing problem. I strongly recommend against installing unmodified E32 bushings by spreading the mounts. I would not feel comfortable in a car that had these highly stressed mounts bent.
Check out the pictures below.