Essentially there are 4 types of brake disc:
You also get hybrids of usually 2 of the above, in those cases,
just combine both the pros and cons into one.
Exactly as you have on your car as standard, flat faced discs. They have more surface area touching the pads when the brakes are applied so initially have better braking power.
The problem with normal discs is that as they heat up you can get a build up of gas between the pad and the disc which causes brake fade and pad glazing. The extra heat can also warp the discs if they are poorly made or have been paired with inappropriate pads.
The face of these discs are drilled all the way through mainly to increase surface area so they can rid themselves of heat quicker. The holes also go a little way to stopping the gas build up that causes brake fade. The problem with drilled discs is that the holes can have a tendancy to start cracking and collect dust and debris.
This picture is of a motorcycle disc but the idea is similar on the car discs.
I do not recommend using drilled discs as they are prone to cracking.
The face of these discs have diagonal lines cut into them, there are two reasons for this.
Firstly they allow the venting of brake pad gasses thus eliminating brake fade.
They also eject brake pad dust to stop glazing of the pad. This keeps the pad face fresh allowing better braking. The problem is that grooved discs have a tendancy to be louder when the brakes are applied due to the scrubbing of the pads.
Discs with grooves should be installed a certain way round. As the disc rotates in its
normal direction, the groove should be spinning outwards. This allows the brake dust
to be ejected away from the hub. Putting them on rotating the wrong way can allow
the brake dust to accumulate in the centre of the hub.
The dimples in a disc clear debris from the pad but the main reason is to reduce weight.
Combinations And The Unusual
Drilled and Grooved
A very common combination.
Wavy Edged Grooved and Dimpled
The wavy edge is supposed to cause turbulance around the disc to increase cooling.
These are primarily sold by a company called Rotor.
Custom Brake Discs
You can go for run of the mill discs, your standard drilled or grooved (although I don't recommend drilled discs). You can also get custom discs made up.
These are custom milled on the face side and standard long grooved on the back.
Because of the long groove these discs are quieter than normal grooved discs.
If you want a set done (NOT with Evilution written on them please) click below.