From BMW website (
http://www.m-power.com/_open/b/varli...lang=en&x=2807 )
quote: 'The 17" sports brake is installed in the car (M135i) as standard.'
The M performance brakes are 18 inch, and thus 1 inch larger than the standard M sport brakes on the M135i.
Also confirmed in real life test by ALPINAB12COUPE57 in the above post
