I just added this to the wheel database in the sticky.
This will be a controversial wheel fitment. We are using an Enkei wheel designed for the front of a C6 Corvette on the REAR of the BERK 135i.
The wheel is an Enkei NT03, 18x9.5 +58 offset, 5x120.65 PCD, 72.6mm center bore.
The BMW uses a 5x120 PCD and a 72.6mm center bore. So the wheels are a perfect hubcentric wheel (go figure) but the PCD is ever so slightly larger than the BMW, so each bolt hole will be 0.13mm off center or 0.005in. Just remember to use them at your own risk!
We tested this setup with the fenders rolled by an amatuer (me) and we didn't have any rubbing issues during normal driving. We were taking this car to a Time Attack race event and I needed to be extra cautious since the car would see even greater suspension compression with banked corners, stickier road surfaces, and zero speed limits. So we had the rear fenders rolled with a proper tool before the weekend. (Side note: read about our weekend here:
http://www.1addicts.com/forums/showthread.php?t=246926)
I believe Enkei is going to discontinue this wheel so we plan on picking up a few extra sets just in case.
The front wheels we are using is a standard BMW fitment that Enkei already offers, a 18x8.5 +38 5x120. Also hub centric to BMW so no hub rings are needed. These could also be used on the rear of the 1er. It's very close to the non staggered D-Force Empower 18x8.5 +40 setup that we run our practice tires on. Ralph runs this non staggered setup on his 135i race car. He could upgrade those rears to this setup if he wishes.
The wider rear tire on a proper 9.5" width wheel REALLY helps with rear end grip. From a performance standpoint you DO NOT want to use a 265/35/18 on a narrow 8.5" width wheel. I have seen people doing this here. Running a wide tire on a narrow wheel is very detrimental to performance. Keep within the specs of the tire manufacturer wheel widths when mounting tires. So for a 8.5" wide wheel, a 255 would be the max.
The Cliff notes version of what I'm saying here:
The rear wheel setup is not a true BMW setup. We use it without any issues but USE AT YOUR OWN RISK.
Wheels: Enkei NT-03
Front: 18x 8.5 +38
Spacer: 5mm
Rear: 18x 9.5 +58 (Hub centric to BMW but with a 5x120.65 bolt pattern from a Corvette)
Spacer: none
Tires:
Front Toyo R1R 255/35/18
Rear Toyo R1R 265/35/18
Suspension/Fender Mods/Camber:
KW Variant 3 Coilovers w/ HP Autowerks Springs, Vorshlag Camber plates @ max neg camber.
Front fenders rolled slightly.
Rear fenders rolled with a proper tool as of 03/09. (No more baseball bat!)
Approx 2" strip of the liner has been cut out in the rear.
Notes:
Rear is VERY LOW. No rubbing on the race track or during regular street driving. I was able to get it to mouse squeak of a rub once while going down a very steep driveway but otherwise I would call this a "no rub" setup!
And the disclaimer: Use the rear wheels at your OWN RISK! I have talked to several wheel manufacturers and the bolt pattern size difference is small enough that no machining is needed, but it IS NOT A BMW 5x120! Make sure the wheels balanced properly and you are using STEEL lug nuts or lug bolts with the proper torque. I use 90ft/lbs in the rear and 85ft/lbs in the front.