Are you having issues with your brakes squeaking? Is it time for a replacement or are they fairly new?
Let's start with the possibility that they need to be replaced. Often the manufacturer of your brake pad will add metal clips that cause squealing or squeaking to occur when the pads are worn. If this seems to be the case, time for new brakes. Here is a quick part list of what you will need:
PADS. You need to select a pad that works well for how you drive.
Semi Metallic: more aggressive and more stopping power, but more noise and dust.
Examples: Hawk HPS Street Sport, ATE Original Premium One,
Satisfied GranSport GS6
Ceramic: less dust and noise, but not as aggressive bite and stopping power.
Examples: Akebono Pro ACT, ATE Premium One, Hawk Performance Ceramic
ROTORS. More than likely you will need rotors. It is recommended that you do not turn your rotors, but replace with new ones. A rotor's effectiveness is based on dispersing heat, and taking any metal away will diminish its ability to do such.
Solid: Normal driving to autocross racing (parking lot with cones/markers)
Centric, Cryo-Stop, Brembo
Slotted: Extremely aggressive driving to road racing. (large, repeated speed changes)
ATE, Power Slot, Power Slot Cryo, Brembo, DBA
FLUID. If it has been 50+ thousand miles or you drive your vehicle hard, you may consider flushing your fluid. If you fluid looks like coffee or tea at the caliper end, time to flush.
So if you are the type of person that decides to change the brakes on your BMW 335i and are looking for an added edge, this is a project you can do! Remember when you upgraded to the Michelin Pilot Sport PS2 tire? Choosing the right brakes will make the same difference for stopping as the difference the right tire makes for cornering!