After 300,000km, the old suspension was no doubt a little on the tired side. An easy fix is to fit a set of adjustable suspension. So, that’s what I did.
I noticed a few times when out on the back roads having a hoon, going over some harsh bumps the front shocks would bottom out. If you have ever had a shock bottom out, you will know how ugly this feeling is.
For the most part, the suspension rode well, but body roll was out of control. The shocks were obviously far too soft.
A set of barely used BC Gold adjustable coilovers popped up on Facebook, so I had to grab them. I previously had a set of BC Golds in my WRX RA and really liked how they rode. Firm, but still compliant.
I had them sitting in the garage for a while after having them sent down, but I bit the bullet the other week and threw them into the car.
The set consists of two front shocks with coilover springs (hence the name, “coilovers” as the spring is over the shock), two swaybar links, two rear shocks, two rear springs and two adjustable perches for the rear.
The BMW uses a divorced spring setup in the rear, where the springs and shock are separate. This is a pain for setup and dialling it in, but does work. You can convert to a true coilover in the rear, but this requires special reinforcement as the strut tower in the rear isn’t designed to have that load on it.
Then I went around the car and measured the current ride height. This was measured from the centre of the wheel roundel to the highest point of the arch. Because my driveway is at a steep angle, I already scrape the exhaust coming in and out, so lowering the car further is basically a no-go. I needed to match the current height. A small strip of tape and a pen allowed me to mark it down.
Zip off the top nuts (once again, the cordless ratchet made light work of the limited space), and the shock should drop down. Now remove the single bolt at the bottom of the shock. The shock can be removed now.
Removing the spring can be a pain. The easiest way I found, is to hold the spring in one hand, and pull on the spring whilst stomping down on the hub to push the lower arm downwards. This releases the spring and allows it to be pulled out.
The new shock and spring go in basically the same, except for the spring perch. This is a good time to fit your new Z3 strut tower reinforcement plate on the top before you fit the shock top nuts. There are some differing opinions on this, but I chose to mount the perch above the spring to allow better access to the locking rings, but some people mount it to the bottom arm.
I reused the upper and lower rubber pads from the original spring. Setting the height and preload on the rear is a real pain, so head over to Youtube and search for how to do it on there, as there are a couple of good videos about it.
All the locking rings were left loose as I had no idea how low the car was going to be once it was on the ground and it would need tweaking.
The fronts are a fiddle, but a bit more straight forward to install being a single coilover. Three nuts on the top of the strut tower, two bolts on the bottom of the strut, and one bolt that passes through the knuckle hold it in. On the M3 the swaybar link mounts to the strut, so that needs to be disconnected too (mounts to lower arm on all other E36 models). The strut can then be removed. This will allow the whole knuckle/hub/brake etc to flop around freely, so make sure it’s supported and not hanging by the brake hose.
There is some setup to do on the front shocks. One is that the strut tower reinforcement plate needs to go on the top before it’s mounted up (goes under the tower unlike the rear which goes on top). This is cheap insurance against strut tower mushrooming (same as the issues on the BMW built Mini). As it turns out, my drivers side had already started to mushroom, but fitting the reinforcement pulled it all back into shape, and should stop it happening again. These plates were fitted to the 96+ M3 Evo, but not the early ones like mine.
Wind the bottom ring up and lock the two together. Your pre-load is now set.
I tried to set the new shock to the same length as the original shock, thinking that I should be in the ballpark of the original height. Boy was I wrong; I didn’t realise how much the old shock sank with weight on it.
It ended up settling about another 1cm overnight, so was 2cm too low now. After a lot of messing around, I got the heights pretty close to the original measurements. Much raising and lowering the car, and wheels on and off ensued. Not the most fun process.
Everything was torqued up and locked down, and it was time to try the driveway. I guess its due to how stiff the new shocks are in comparison, but even with the rear being slightly lower, it doesn’t scrape at all now. Very happy with that result.
On the road, the results are pretty clear. I set the damper stiffness to about half, and at that, the car handles well but almost glides over bumps. Its a lot better at damping bumps than the old stuff, and contains the body roll much better. Very happy with the ride quality of BC Golds again. A+ would trade again.