[tetsuo111]

Originally Posted by Biginboca

Aww man, so bummed to hear you still fighting these electrical gremlins. I’m sure that’s super frustrating!

As long as I have your attention, quick question. You show your running a M3 rear spindle and hub. Did you have to modify the rear 328i axle shafts or do they fit the M3 hubs no problems? (I assume you are not running M3 axle shafts.)

Per RealOEM:

1. The bearing, labeled #2, is the same part across all 3-series chassis, including the M3. The 328i axle shafts fit these hubs PnP, just as the diagram illustrates.

2. The hub, labeled #1, is unique to E90 and E91. Furthermore, the part applies only to non-M platforms. The M3 hub differs from the non-M part. If you choose to use M3 brake rotors, then it requires the M3 hub or else significant modification to the M3 rotor. This is due to the positioning holes on the hub face and rotor disc.

3. On my car, I use the universal bearing (part #2) and the M3-specific hub, together with M3 spec brakes and M3 spec dampers. This setup requires no modification of parts to fit on the non-M E91 platform.

4. Given the above, to my eye, the rear offset / wheel placement appears mildly "inboard". In other words, visually it looks like the rims could use a lower offset spec, or perhaps the M3 drive axles or M3 LSD differ from the non-M such that the end result of my configuration is mildly inboard rear wheel sets.

5. I'm addressing the inboard appearance by adding 5mm spacers.

6. There might be a better way to do this, but I haven't figured it out, and I doubt I'll apply more cycles to this project. Getting PnP within 5mm of the correct offset is good enough in my way of thinking, rightly or wrongly. On the plus side, everything on the rear is OEM PnP. Everything is OEM or OEM+ M3 suspension and brakes.

7. In summary, my sole unknown is the rear track width. This bothers me. A lot. If there was an easy way to accurately measure rear track width, I would do so. Instead I'm left with going by "appearance", and that isn't my preferred method of working the problem. At the end of the day however, I'm satisfied with the result. I'm coping with rear offset using reasonable spacers, and everything else is OEM PnP M3.

I hope this helps a little, Al. Ping me again and I'll do better at replying. Have just been focused on work. Cheers!