Are you guys talking about front or rear? I think LCI E90, E82, and E92 M3 all share the WIDER rear track width and you can convert to the old (pre-lci) e90 hubs to gain ~8-10mm clearance to the fenders (narrower rear track width). Maybe there are more asterisks/exceptions attached to that statement though as I see some ppl saying 4mm per side for some cars? Old style rear e90 spindles are somewhat plug and play.
Rear hub swap parts (per this thread:
https://www.1addicts.com/forums/show...75919&page=4):
2x E91 Performance Rotors (Dimpled and Slotted) 324x22
2x e9x Rear Hub PN: 33416760058**
2x Rear Wheel Bearing - PN 33416775842
2x Axle Nut - PN 33411133785
I really don't see why anyone would waste their time doing this "mod" though as the rear fenders are still your limiting factor and all you are achieving is the same thing a higher offset wheel does. Net scrub radius stays exactly the same. The only real advantage here is that you open up wheel fitments by 10mm lower offsets and open up caliper fitment by a hair when using wheels that have a tapered barrel like stock wheels do. Not significant enough of a change in either regard to warrant all this work. They make plenty of 1-series specific fitment wheels with high offsets. OP has the 1M front-end and stock rear-end so this mod is no benefit to him. He needs rear flares so that he can widen the rear track width back up to match the front.
The rear E92 M3 spindles are NOT exactly p&p. I don't know exactly what you would need BUT You would need complete spindles, down to the calipers and e-brake equipment all from the M3. Not exactly a big deal since they can be had for cheap as complete spindles. What would you gain by moving to the E92 M3 rear spindles? Not much. The axles are different (bigger). The calipers are and rotors are larger but also much more expensive and heavier! Suspension kinematics are slightly different for sure as well (M3 rear toe arm has slightly different pickup point on both the spindle and the subframe). If you get the M3 lower camber arms then you also get the benefit of the M3 style rear strut mount. Just changing to M3 spindles wouldn't really be worth it imo. Go for the entire rear end as the subframe, diff, axels, and strut mounting is the real benefit out back.
On the front, I do not think there is any difference in the offsets of any of the spindles. There is no doubt though that the 1M/M3 spindles are NOT the same and they are NOT plug and play without other components. The front struts mount differently and the tie rod mounts in a significantly different place on the M3, hence why the 135i needs to change it's inner tie rods when using the E92 M3 steering rack. This likely changes bump steer characteristics but not sure how exactly. The multi-link suspension BMW uses makes it difficult to speculate. Even the previous E46 generation suspension was much more simple. I would still like to map out the pickup points in wingeo or something but I never got "before" measurements to compare to so all I'd be able to do at this point is plot the M3 suspension kinematics. E92 M3 front spindles would also obviously require the M3/1M calipers and rotors (larger caliper bolt pattern). They have larger pistons, yes, but also heavier by several lbs and MUCH more expensive. E92 M3 rotors go for ~250/piece ($1000 all around). E82 BMW performance rotors can be had for like $350 all around. I imagine the lighter mass, fixed calipers, large aluminum heat sinks, greater piston count, and larger brake pads that the 135i comes with help offset to some degree the fact that the rotors and pistons are smaller. Real world performance, in terms of braking, is likely much more equal than these forums speculate and I'd give the "feel" advantage to the 135i by far. I can update you on that soon as I already have the E92 M3 rear-end and I am now installing the E92 M3 front pieces. Spindles, brakes, struts, etc. I speculate a lot of placebo affect in terms of braking... mushy pedal with a much more "on/off" feeling which will lead me to believe the brake are better but reality is they are just harder to modulate and same or slightly better stopping distance. Depending on how they end up feeling, I may install the M3 master cylinder to gain back the loss in pedal feel. Overall, I don't anticipate much performance difference but My driver side wheel hub was bent so I decided to pull the trigger on completing the 1M swap as there are the aforementioned benefits.