Nish90 E90 Build

[Nish90]

Hello everyone!
I hope this is an ok spot in the forums to post this, as I think this will be the best place to track my progress and ultimate downfall of watching this street car become a track car. I’m starting my build to turn my E90 into a compromising dad car that sees track time. Or maybe the other way around, we all know how fast this downward spiral works. After my S2000 motor went I decided to part it out and start fresh with my M3. Long story short, I had an S2K and did some track days before I stumbled upon a roots supercharger. After installing it on my car spending lots of money to do it right and taking it to the dyno, the motor developed knock and my patience with that car had run out. I was in between selling either my M3 or S2K so this made that choice abundantly clear. Ironically, the S2K market is crazier than the E9X market, so a part out net me most of my money back. I know I’m going to get the question of how different the cars are so I’ll say the M3 feels like an S2k with a suit on if that makes sense. The primary track that I will be going to is the Ridge in Shelton, WA. I never officially timed myself but while the car was N/A I would lap around the 2:00-2:02 range.
To start off, I've had my car for over a year now. It is a DCT and has 103k miles done. The throttle actuators, rod bearings, VCG, and DCT service were done approximately 20k miles ago. It has relatively new (~1500 miles) Fortune Auto 500 coilovers with 11k/13k Swift springs. It is not a daily driven car so I am not worried about harshness or the quality ride. I am mainly interested in parts that are strongly recommended for track duty to ensure safety and reliability. This is more for enjoyment/stress relief than anything and I don’t plan to run in a particular class (yet). I have purchased Recaro SPGs, BW solid subframe mounts, KMP dct wheel, Paragon bbk front and rear with their R5 pads, and 18x10 +25 ZE40s. I’ll admit the KMP wheel, Recaros, and ZE40s are vanity parts but you’ve got to look good too, right?
In the near future (next few weeks) I plan on purchasing Core4 hubs with 14mm studs, BW solid diff mounts, some form of roll/harness bar that I can remove in between track days, and Domi-Works billet dct covers. I know removing a roll bar in between track days may seem like too much work but right now I only plan on 5-10 track days a year and I would like to enjoy this car off the track with my son who is three. I don’t think it is safe to leave him strapped in the back seat in between a bunch metal bars, nor do I think a car seat would fit inside of one. Maybe it would fit in the center seat with a Studio RSR half cage? But if someone knows of one that can make that work that would be neat, still don’t think I’d leave him back there though. For maintenance, I plan on all new fresh fluids, spark plugs, maybe coil packs, power steering reservoir mod and potentially vanos covers.
I’m posting this up here to track this build like everyone else but would also like some feedback on what should be next. Some of my concerns are the driveshaft flex disc and center bearing. I don’t have noise or clunking but I know this could be muffled by the oem bushings. I have thought about the carbon driveshaft but I also read some threads having issues with a carbon driveshaft. I’m not sure what mounts for the trans and motor or if it is even required above OEM quality. Again, I’m not too concerned about harshness or NVH. The spring rates I’m currently on 11k/13k for a full weight car but I think after a season I will switch to a higher quality damper like MCS or Nitron. I want to get used to the car before I change too much and this doesn’t seem like too much of a safety or reliability concern to me. I think all the control arms are original to the car but they don’t look rough and I don’t see any rips or tears. I think I will pay close attention to these after each track day to monitor for failure and replace with OEM as needed. For tires choice, I’m leaning towards a Nankang CR-S since they’re cheap and have good enough performance. I did have RT660s on my S2K and I really enjoyed them but narrow 17” tires are much cheaper than 18” 275s. The last item I could think of is a DCT cooler from D088 but not sure if that is completely necessary at this time.
At the moment, I am not concerned about saving 20lbs here and there or gaining horsepower so the intake, exhaust and tune will stay stock for now. I don’t want to do an aero package yet so I get used to the car first before I can really come close to feeling the car at the limit. The lip that is on it now is more aesthetically pleasing than anything. My goal is to get more seat time and experience but I want to ensure I am safe, reliable and have fun while doing it. I’ve been creeping around the track section of the forum for some time and any insight or recommendations would be greatly appreciated!

[elliotw44]

Gonna be a great dual purpose car. The ridge is a very fun track.Hopefully I'll see this out there. I'd personally skip a rollbar on a sedan given you want to keep it for both street and track.

[b4hand]

A good seat time tire are the Hankook RS4's. Good amount of grip with a very predicable grip profile.

[Nish90]

elliotw44 I would like to run harnesses for track days but if it's not feasable then I will most likely skip this part. As it is, Studio RSR has an 18-20 weeks lead time. There is the Brey Krause option too but I've never been much of a fan of a simple harness bar.

b4hand I have looked into the RS4s too as they have good reviews. I'm sure with how heavy these cars are, I will have plenty of chances to try new tires!

[DRLane]

Originally Posted by Nish90

elliotw44 I would like to run harnesses for track days but if it's not feasable then I will most likely skip this part. As it is, Studio RSR has an 18-20 weeks lead time. There is the Brey Krause option too but I've never been much of a fan of a simple harness bar.

b4hand I have looked into the RS4s too as they have good reviews. I'm sure with how heavy these cars are, I will have plenty of chances to try new tires!

I’d go Brey Kraus harness bar over the rsr roll bar especially for a sedan. All the restraining benefits and none of the downsides.

[okusa]

Originally Posted by Nish90

elliotw44 I would like to run harnesses for track days but if it's not feasable then I will most likely skip this part. As it is, Studio RSR has an 18-20 weeks lead time. There is the Brey Krause option too but I've never been much of a fan of a simple harness bar.

b4hand I have looked into the RS4s too as they have good reviews. I'm sure with how heavy these cars are, I will have plenty of chances to try new tires!

I have an E90 half cage for sale if interested. Can still fit 4 wheels in back if needed.

[Nish90]

DRLane I think you might be right. The lead time on the RSR half cages are 18-20 weeks anyways.

okusa LA might be a bit too far of a drive and I can only imagine shipping costs even to Washington would be insane. I appreciate it though!