Replace the rotors or can they be machined?
 

Well, I have an 06 4.4 with 57k on it and the rear pads and sensor need to be replaced. I have replaced the pads on my 01 530i and my 95 M3 before. Well, I have researched the forum and have read a few things in other places, but can't really seem to find something about if i can get the rear rotors machined? I have heard the rotors will be fine if I have enough of it left, 10.5 I beleive. However, the dealer says replace them fully. I obviously want to do it right and at the same time, not waste money if I don't have to. I have gone to a "popular" bmw part store online and they are looking at 108 for each rotor. An auto parts store will machine each rotor for 15 bucks. I have the time, but I need a few opinions here. The stealer said 644 bucks for rear pads, rotors and the sensor. lol. what a joke.

You should not machine the rotors as they have a compound that is machined away and reduces their performance.

I had to do a brake job, and rotors were all in spec so i had them machined for $10/each. BMW and almost every member will recommend not turning your rotors, however if they are still in spec there shouldn't be an issue. However, it did take me considerably longer for my pads to bed in completely. After that, perfect.

If you want to do it right, buy new rotors, if they are still in spec and you'd rather turn them, there should be no issue for you, yes you can.

BTW the compound that they speak of is just an anti corrosion coating, paint the none friction part of the rotors if that's an issue, it's just a visual thing.

you can machine the rotors and the coating on the rotors is just for rust prevention

front pads should cost no more than 95.00 dollars. rotors sould run you 100.00 dollars a piece and thats the good quality ones like zimmerman or a brembo.
rears are 85.00 dollars for pads and the rotors are 92.00 dollars. mind you in in toronto and we have tons of small parts store's and we can get some good deals .the pads that i used are pagids the same that the dealer sorry stealer would use.

Depending on the current thickness of your rotor will really determine if the rotors can be machined. The tolerance BMW gives for the service life of the X5 rotors is not very much. More than likely your rotor thickenss minus the material that must be removed to provide a clean flat surface will be more than the service limit on the rotors. Sure, your car will stop fine in the beginning with new pads, but as the pads start wearing down, the caliper will be working that much further to make the pad contact the rotor.