Okay let me start with jts1981's comment, and talk about suspension changes. I'm concerned - he puts a bunch of smiley faces at the end of his KW comment ... but reality is he has been right many times so I fear he'll be right on this too :-(. But for now, here's where we are on suspension.
I tried to avoid coil-overs. I didn't feel they were necessary for the street, but I felt some work on the suspension should be done to help deal with another couple hundred horsepower. My setup, from the
spreadsheet, is ...
H&R Springs
H&R Sway bars
Luxon front strut bar
AKG spherical bearing front tension strut
BMW E9x M3 front lower control arm
Rear spherical rid sway bar end links
BMW E46 M3 trailing arm ball joints
E46 M3 RTABs
RTAB limiters
Forgestar F14 wheels, 19x9 ET35 & 19x10 ET38, bronze burst finish (jts1981 to thank for the specific wheel/tire setup that works on this car)
Hankook Evo v12, 245/35-19 265/30-19
Most of this has been straightforward. I want to share a few observations:
- The rear suspension is E46 based. The upper rear controls are slightly different, though. They are stamped instead of the old cast aluminum. Specifically the rear sway bar link mount is slightly different, which leads us to the next comment.
- The H&R rear sway bar has 3 adjustment positions. We could not get range of adjustment with the factory end link. Furthermore, with the suspension fully unloaded, the bar hit the half shaft. In our book this is bad news. Not that we drive around with the suspension unloaded, but understand in spirited driving it is easy to even over extend the suspension. So this led Barry to source pieces to make rear sway bar end links which now give us adjustability and clearance.
- The dread Rear Trailing Arm Bushing (RTAB). If you decide to buy E46 limiters and stuff them in there. Good luck. The E89 RTABs are ostensibly the same dimension, but the German engineers figured out that deflection could be reduced by extending the rubber 2mm on each side of the bushing (4mm total). So limiters will not fit without removing 2mm on each limiter. That's ok because the E89 RTABs are not the M3 version ... so the simple solution is to push out the E89 RTAB and install the E46 M3 RTAB which is more sturdy, and then the limiters simply fit - two birds killed with one stone.
- There is a heavy, steel damper mounted to the rear trailing arm. I've pulled it ... we'll see if it makes any difference I care about.
- Lower ball joint on the trailing arm is rubber ... E46 M3 slides right in as a ball joint
- The Luxon front strut bar is the only one I've seen for the E89, and thankfully it is fixed (versus adjustable/flexible). It comes from South Korea, oddly ... check out eBay.
- Rather than go to the E92 M3 tension strut arm, I decided to press in the AKG spherical bearing.
- Forgestar did a great job on the wheels - they were a bit tight on the rear hub centers, but a bit of grease and they are good. Reasonably priced for what they are.
- I ended up with Hankook Evo V12 tires - I had tried to get Yokohamas (my preferred tire) but they'd been out of the country for 6 months. The newer V12 had good reviews, though honestly if they turn out to have issues, I'll punt them for a different tire. These came mounted from the wheel provider.
So that's the bits on suspension for now.
Filippo