M Coupe Suspension Overhaul

Much like any 10+ year old suspension, my M Coupe’s had seen better days. Well that’s not entirely true, considering it only had 30k miles, it’s really in pretty pristine condition. But mileage and age don’t always take parallel paths when it comes to vehicle components, especially when it comes to seals and rubber. Rubber hardens, dries, and gets brittle over time. Seals also dry up, slow leaks form, gas pressures in shocks go down, so on and so forth. Often times low mileage can be your enemy, as an idle car doesn’t have the various oils and other necessary fluids flowing to keep seals pliable. I had already replaced the engine mounts and nearly every other piece of rubber, so now onto the hard bits.

Another good reason to upgrade the suspension bits is due to the very soft suspension setup that came standard on the M Coupe. While I enjoy a cushy ride, this was a bit much. The car would pitch quite a bit under throttle (aka squat.) I wasn’t after a rock hard race setup, actually nothing close to it. I just wanted something slightly more performance oriented. The general consensus across the Bimmer forums is to go with TC Kline, who has a great deal of experience in dialing in BMW suspensions. They use Koni shocks, another plus, and perhaps the best part is TC himself answers email questions. I debated back and forth between the Single Adjustable (SA) and Dual Adjustable (DA), finally settling on the SA for the price vs. performance. I simply didn’t need more. I also went with relatively soft springs 350f/400r. Still stiffer than the oem springs, but no where close to a race setup. The setup came with height adjusters for the rear and rear shock mounts (RSM) also.

To complete the setup you can either reuse your stock shock hats, get aftermarket camber plates, or like I did; just buy new strut hats. I opted for new OE, because it uses a rubber isolator, rather than a spherical bearing like found in a camber plate. Remember I’m trying to maintain a stock-like level of NVH (or better.) Buying new allowed me to keep my stock struts together, no need for a spring compressor. The TCKline RSM are virtually identical to the Rogue RSMs, which allow you to bolt the shocks in from the wheel well, rather than removing all the interior.

While I was redoing the suspension, I also replaced the OEM front control arm bushings (FCABs) with Powerflex street bushings, which I picked up from Bimmerworld. Good luck pulling the old FCABs off the arms, I resorted to a puller. The little bit of rust scale makes them really cling on. I cleaned them up with some sand paper afterwards.

Getting the old bushings out of the brackets will require a press. Easy enough with my piece of junk Harbor Freight 16ton press.

Old and new bushings beside each other. The Powerflex bushings are actually two separate pieces. An inner black insert is of much harder durometer than the purple insert. It’s almost Delrin like in its feel. A flat washer goes on the arm first, followed by the black insert. I used a pipe to drive the bushing onto the arm with some light tapping from a deadblow. Powerflex includes a small packet of lubricant, to be applied between the two bushings. The rest of the assembly goes together by hand, simple stuff.