E46 M3 Suspension Refresh

At 136000 miles, my M3's suspension was tired. Beyond tired. The ride of the M3 should be taut, well controlled, and confidence-inspiring. Mine was loose, uncontrolled, and decidedly un-inspiring. I have a new commute for work starting soon, so I decided to get some work done. I'd really like to go through the whole suspension and replace all the bushings but the most pressing issue was the shocks and struts. The OEM suspension on the E46 M3 consists of non-adjustable shocks (rear) and struts (front) made by Sachs. They are very high quality and well suited to the M3 in street form. For my upgrade, though, I decided to go with Koni Sport adjustable shocks and struts. They're very affordable (cheaper than the Sachs) and have been the go-to adjustable shock in sporty-car circles for decades. I have no desire to lower this car, and don't see myself tracking or autocrossing it any time soon. I will be taking it for many spirited drives in the mountains, since the legendary roads of the East Tennessee and Western North Carolina mountains are just a few miles away. So, I figured the Koni's and stock springs offer the best combination of sporting character and affordability. I ordered them from ECS Tuning on a 20% off sale and got them within a couple days.

I also ordered new top strut mounts and reinforcement plates. The plates are an OEM BMW part that is meant to prevent deformation of the strut towers. Mine were showing no signs of any issues so I guess I didn't need them but I suppose they can't hurt.

Getting the strut out is pretty straightforward. You disconnect the swaybar link, remove the bottom clamp bolt and wiggle the strut out of the spindle. Mine were quite stuck and I had to use a drift and a rubber mallet to strike the top of the hub and work the bottom of the strut out. Then you remove the three top mount nuts and the whole strut will fall out. The original strut, once out, is disassembled using spring compressors so the springs and a couple washers can be reused.

Assembling the strut with the Koni shock requires a little ingenuity. The top of the shaft is 11mm hex, which you have to hold in order to keep the shaft from spinning while you tighten the top nut. You can see how I solved the issue with a 1/4" extension and a spark plug socket with flats that allow the use of a wrench.

Once the strut is assembled, getting it back in is quite tricky. It's a Chinese puzzle and nothing I write here will help you.

The rear shocks are easy to get out and easy to assemble. The Koni rear shocks have a 5mm hex socket on the head which you can hold with just an allen wrench while you tighten the top nut with an open wrench. I had to reuse the bump stops because I neglected to order new ones. They look bad but seem to be serviceable. I used new top mounts and also bought the ECS rear shock mount reinforcement plates.

Installation is super simple. One bolt on the spindle and two nuts in the trunk.

The top mount with the reinforcement plate. There was no apparent issue so I probably didn't need the plates, but they're cheap.

I tested the old shocks by compressing them by hand. They were very easy to compress and the rears would barely re-extend at all. The fronts were a little better but not much. The new shocks are set at full soft in the front and one turn up from full soft in the rear. This brings me to the one major drawback of the Koni sports. The rears can only be adjusted for rebound by removing them from the car! You have to compress them completely and then turn the shock body in relation to the shaft. The fronts have a knob on the top for the adjustment, so no big deal to make changes to fine-tune the ride, but if you are an autocrosser or track star and think you may want to make frequent adjustments you might want to look for another solution.