At least one other person and I having same problem with M3 CSL as you report with Z4. Afraid to try Racing tires. Given religion by Praiano's lecture re proper tires for car type.
It's first car I tried on GT6 'ring so I don't know if it's car or track, but I find you need to feather brakes a certain points on track far before I would have even slowed with other cars here back in GT5. I must be much more careful than usual with not braking, downshifting, or even just taking foot off gas able to spin this car at some points if not in perfectly straight line. Perhaps due to not noticeable rising, falling, tilting of track? Much better now I have memorized places where special care is required. Absolutely cannot trust gear suggestions or blinking lights (usually so conservative) to warn me.
Regards,
Rick
Last edited: Dec 22, 2013