[ska///235i]

M Sport brakes: fixed calipers, four-piston front, two-piston rear, large brake discs. Made by Brembo.

The regular bmw brakes are floating calipers with 1 large piston.

Is it worth it..yes, its a bargain to upgrade thru options. In real world street driving, the msport brakes are alot smoother. On track, more resistant to fade. Another benefit is that the floating caliper has a sliding pin (to float the caliper) and if not lubricated correctly will make sqeak noise.

Some Info on Fix vs Floating Calipers (im just copy/paste from someone)

The more even the pressure on the pads, the smaller the risk of the pads chattering and the better control you have over the pads.

Most brakes today are floating caliper, single-piston designs, though a few use floating caliper dual piston designs.

On a floating caliper setup, the piston is on only one side of the caliper and the caliper itself slides slightly side to side on pins. Fixed caliper setups have pistons on both sides of the caliper and the caliper does not slide at all. Fixed caliper setups provide more even brake pad wear than floating calipers and also provide more consistent pressure between the two sides of the caliper because this setup does not rely on the caliper's sliding.

Fixed caliper designs, of course, require at least two pistons; one for each side.

Larger pads provide a greater swept area which means a greater area over which heat is generated. Because the total heat for a given stopping force is always the same, greater swept area means better heat dissipation and less brake fade. Having multiple pistons per side helps apply more consistent pressure over the entire surface of the pad which not only allows the larger pads, but also reduces chatter and flex, both of which generate additional heat as well as reducing overall brake feel.

So, while a one-time emergency stop will not show much difference between a single piston sliding caliper and a 6-piston fixed caliper, the multi-piston fixed-caliper design will be more resistant to fade over several hard stops in quick succession.