calliper
 

when i brake there is this grinding sound, and i think the callipers are sticking, my question is do i need to buy new ones? or do they just need to be pushed open?

Depends. They may just need to be rebuilt and replace the bushings and guide pins.

could also be your pads are worn down to the metal. Have you checked them lately?

Could also be a small stone caught between the dirt shield and backside of the rotor.
Could also be the dirt shield scraping the back side of the rotor.

ok how true is this statement. "your rotors are throw away rotors, you should change them every time you change your brakes..." is what i was told, and i think it total bull****?

unless you're on a tight budget, always replace pads and rotors at the same time

It is 100% true... When I install new pads I install new rotors... always.

Depends.

I can understand a dealer or independent wanting to change rotors at the same time.
When replacing pads there is a possibility of pad deposits on the rotors causing a shuddering when braking. Now the dealer needs to replace the rotors and eat the labor because no one is going to believe them when they explain that there are pad deposits because you used two different brake compounds.

Doing the entire job at once allows them to guarantee their work.

On the technical side, this is probably true. Manufacturers are no longer making rotors that are thick enough to be turned (or resurfaced) when you change your brakes. Most rotors today are being cast near minimum thickness to save material, rotating weight and increase fuel economy as much as possible.

well thats good knowledge for the future. on the other hand i have good news, i've found out why my car makes a wallet clenching grinding sound everytime i touch my brakes. ive managed to grind down my driver side rotor (the other side is perfectly fine?) to the point where it looks like a quarter thats been kicked around a parking lot... if anyone has some obvious advice for me since i'll be replacing the rotor tomorrow id be much obliged :)

the caliper might be sticking causing the rotor to wear more on one side, put some kind of lube on the sliders and it should be fine

Replace both sides.

Check the piston edge for corrosion plus check the seals around the piston for deformation and corrosion. If the seals are gone but the piston is okay you may be okay with a caliper rebuild (clean-up + new seals), but when the piston is out check it thoroughly for pitting and scoring, if so you'll need a new piston (not available from BMW so you may find it easier just to buy a rebuilt caliper). If you just force it back you are delaying the inevitable, which I found the hard way.

they always say go big or go home...? :S <br>http://img.photobucket.com/albums/v3...a/P6080182.jpg