Background
For those drivers not satisfied with the improvements made by using heavier duty brake pads, a number of higher specification brake discs (or rotors for the North American audience) are available from a number of vendors. In this section I shall focus on discs of standard sizes which work with standard calipers and rims.

Upgrade Options
The three main flavours of upgraded discs/rotors are as follows. They should all have increased resistance to warping in comparison to the standard discs. They should also exhibit better performance in being able to either work at higher temperatures or take measures to try to prevent excessive temperature build up in the first place.

Grooved
The improvements made by grooving the disc/rotor is to assist with cooling and dust removal. Also known as 'slotted' discs/rotors. There are umpteen variatons in the marketplace of how many grooves are best, but the hype is that more is better. I'm personally not convinced but we'll never know until a proper S2 'brake-off' test is performed.

Drilled
The improvements made by a drilled disc/rotor are mainly in the area of increased cooling capability which allows the discs to run hotter and longer. Additionally, drilled discs provide better braking performance in the wet - simply because any surface water is quickly expelled through the holes.

Note that all 'drilled' discs are not created equal. Those which have the holes made as part of the casting process are much less prone to the cracking problems that are sometimes associated with machine-drilled discs. The superior method of casting the holes is more expensive than drilling. Consequently some vendors are now manufacturing discs with partially drilled holes to reduce the chances of cracking. These are called 'spotted' discs.

Drilled & Grooved
This is simply a combination of both worlds which is alleged to be superior than each technique in isolation.


Vendors & Choices
There are simply too many vendors and variations of grooved/drilled permutations to capture them all here. What I've tried to do is list all the known vendors and simply state what type of upgraded discs they have for the S2. More part numbers to come - all info welcome - most vendor sites have incomplete online catalogs and I haven't had time to call them all yet !