NOTE: This is on a 540i, not an M5. However, the coils are the same for both cars, so I thought it would be useful to post here.
Here goes, my review of the Bilstien PSS9 Coilovers for the 540i/M5. These went on my 1999 540i non-sport. I've had the coilovers on for about 6 months and 7,000 miles. I've been through 4 suspension setups in total on my car now, ranging from stock, then H&R "sport" springs with Bilstien Sport struts, then swapped to the H&R "race" Springs, now finally to the Bilstien PSS9 Coils. I kept getting progressively stiffer and lower, because my main goal was to get "low", while stiff being functional and able to be good at the few track events I do a year. Comfort was a concern, but I'm a college student, so it was not a top priority. I'm not driving around my grandmother or infants.
I was searching around on classifieds and found these unused from a guy who sold his M5. My main reason for buying these because arguably they are the best coilover made for our cars. I'm sure I don't have to tell you all about the motorsport history that Bilstien has.
As far as performance was concerned, the Race springs paired with the Sport struts were perfect. Stiff enough that they eliminated alot of body roll on spirited drives, but still decent around for daily (pothole filled) driving. But they were simply not low enough for my taste.
Supporting Mods: (For Reference)
* Dinan Adjustable sway bar (on middle setting)
* ACS Type III 18x8.5
* 255/40 Bridgestone RE760 Tires all around
Price: I got mine for something a little over a grand if I remember, but they were "used". From any major vendor you can expect to pay +/- $2,500.
First Impressions: NICE. All the welds, powdercoating, everything looks amazing. Everything feels "heavy", and high quality. Exactly what you'd expect to find from Bilstien and at this price point. Comes with wrenches and a small card on how to adjust the height and dampening. They come with 9 settings (PSS9), 1 being full stiff and 9 being full soft.
Install: Smooth and easy, nothing out of the norm to report. Everything came pretty much ready to go out of the box. I got it done in less than 3 hours, including a small lunch break and semi-constantly getting distracted by ESPN. However that was my 3rd time doing my suspension, plus I had another experienced mechanic helping/distracting.
Height: It's adjustable, but I thought it was worth mentioning. My M5 front bumper is about 4 1/2 inches off the ground. Front wheels are 13inches from center of the wheel to the fender, while the rears are 12 inches center to fender. Compare that measurement with over suspension setups at the following link:
BMW E39 Suspension Survey And I still have room to go lower on the strut.
Daily Driving: I keep these on 7 F/R. Not too bouncy, and on normal driving roads the ride is perfect. Enough to feel the road, without chattering my teeth. My dad drove my car and his words were "Tight and precise". Only person who complains about the way it rides is the wifey-to-be, but I don't consider that a real complaint because she has always hated how my car rides.
Track Day: Put these down to 1 F/R. On a flat track environment, these were awesome. Not body roll, predictable, and simply amazing. Just a little bit of oversteer, but it would grip and grip and then slowly let go, so it was very manageable. Check the picture below of the track day, that picture is going ~30MPH on the very edge of grip. Simply Amazing.
Pros:
* Great build quality.
* Transformed the car's handling.
* The ride is AMAZING
* Shocks can be sent back to Bilstien to be rebuilt
* 0 body roll when put on stiffest setting
* Dampening adjustable
* Can go pretty low.
* Rides like stock (I think) if put on softest setting
* Lifetime warranty
Cons:
* No Install instructions (not a big deal)
* Bought used so no warranty card, not in original box, etc
* PRICE. Expensive if bought new.
* Not PSS10
* No in-car dampening adjustment
Install
Picture is on the lift - I doubt it goes up that high haha.
Ride Height:
Only rubs at full lock: