A few weeks back I wrote that the Bilstein shocks are now available for the M Coupe and M Roadster. Since the stock rear shocks are significantly lacking rebound damping, I ordered a set and posted here that I'd report back.
First, I have no significant car driving experience so take my notes with the usual "it's from the internet" grain of salt.
The Bilstein rears don't noticeably stiffen the ride, but they do significantly reduce the rear end's tendency to come around when you get off the gas or hit a bump big enough to unweight the car. I could tell this was the case immediately and even my brother commented that as a passenger it is a night-and-day difference. Still I wanted to break the shocks in and test them under tougher conditions before passing any judgement.
This Saturday the San Diego BMWCCA chapter held an autocross at our local stadium. I attended, and the shocks performed better than I could have imagined. One quick note: another M Coupe was running in the M Modified class. It beat me by about 10 seconds a lap, running about one second off the pace of the fastest car there. The only mods on the car were R compound tires and Koni rear shocks. The driver probably could've beaten me in a Pinto.
So I'll wrap it up with two pieces of advice. Replace the rear shocks on your M Coupe, and get to any autocrosses in your area. They're more fun than should legally be allowed and you'll learn a *lot* to improve your driving skills.
PS Any M Coupe owners in the San Diego area that would like to drive my car for comparison are welcome to e-mail me privately.