Max tire size on 9x18 rear wheel

[chamilka]

Car: 2000 Boxster base
Wheel: 9x18 Turbo twist Porsche Factory Wheels
Rear suspension & camber: Car has stock suspension & camber alignment.

Currently I have 265/35/18 on the rear wheels.
Qn: what is the max tire size I can install in my 9x18 wheel without having to use any spaces, fender rolling, any rubbing and performance issues?.
Tire preference: Michelin Pilot Super Sport tires. Car will be used in both track and street.

Following are some options, let me know what you think:

Michelin Pilot Super Sport 275/35/18
Michelin Pilot Super Sport 285/35/18

Thank you.
Chamilka