Originally Posted by racingbmwm3 (Post 972726)

etched/stamped on the rotor hat is the minimum thickness. use a caliper to measure the disc thickness at the thinnest area. generally, if there is a raised lip at the very edge of the disc, you need to replace them. My experience has shown that the front discs need to be replaced everytime with the front pads. The rear discs generally can get two sets of pads before needing to be replaced. But, that is all dependent on driving style.
Don't turn your discs as you lose even more disc material and will definitely be under the minimum thickness at that point. This also puts you at having higher chance of getting warped rotors. Cheap new rotors also have a very high risk of warping (if not a guarantee of it).
I'll bet that none of your previous vehicles could stop as fast or with as much control as a BMW either. Think of your chassis/suspension as a whole. To be at the highest level of safety (or grip/traction) you suspension, brakes, and tires all need to be in good condition. Your DSC system relies on all 3 parts to work effectively; or if driving with DSC off, You need all 3 parts for maximum control. All 3 are only as good as the worst component. If you don't care, might as well be driving a Hummer or Escalade...ok, rant over.

Originally Posted by StephenVA (Post 972724)

"I trashed my car but did not notice"

Originally Posted by StephenVA (Post 972588)

Baum Tools - brake thickness measurement tool. No need to remove the wheel, just insert the tip into the back of the brake pad and see the measument in MM. Yes, it is pricy but it beats the heck out of pulling multiple wheels on my stable of of BMWs. 5 mins of effort beats pulling wheels each quarter. Those of you who do this for a living already own one. After seeing one in action, I added it to my Christmas list and ordered it!
Multiple tool vendors sell it, all at the same $$$. Welcome to special tools...
For gauging brake lining thickness w/o wheel removal, PN: 341260
Tool Listing
http://www.baumtools.com/search/_bb_...ges/341260.jpg

Originally Posted by racingbmwm3 (Post 973685)

3mm remaining, which is 20-25% pad remaining. I'd at least do a visual inspection through the wheels to try to judge which brakes (front or rear) are worn by looking at the outer brake pad. Say your pads were last changed 30,000 miles ago and they are currently 80% worn out (20% remaining), you theoretically have 7000ish miles of life left in the pads. But, the lower you go with pad remaining, the more likely you are to start getting uneven wear on the pads and rotors, and possibly separation of the pad material from the backing plate. They are also more susceptible to brake fade during hard stopping from high speed.

Personally, I wouldn't go more than 1-2k miles after the light comes on. This is similar to the tread wear indicators on your tires, those show when you have 2/32" tread left. I try to replace my tires at or just before I get to that low of tread, or go waste the rest of the tread auto-crossing.