Switched the rear wheels out for the BBSs, they have 185/60r15 with second hand ze912s...pleased to say that for the first time ever i can spin wheels from a standstill. Unfortunately I had to mount them on 40mm 5x108 hub and wheel-centric spacers that I just happened to have lying around, because I didn't have the right lug nuts to mount the wheels straight onto the hub (the studs didn't stick out far enough as opposed to the spacer studs which were a lot longer and allowed me to get lug nuts onto.)
....Unfortunately I now have a really bad shuddering vibration that eminates from under the car (and subsequently shakes everything) upon acceleration. I'm suspecting that I need either u-joints, driveshaft centre bearing or something rear end related replaced. The shuddering started happened after I did a first gear clutch dump with the 225/50 semi slicks...the shuddering, clunking and banging has only gotten worse as the days have gone by.
I will be taking it to Lupica Motors tomorrow to get them to get it on the lift and diagnose it for me; hopefully it's not too f'd up underneath.