If you have a BMW produced after 1992, and your brake lining light appears, you’ll need a brake job that will consist of new brake pads and new brake rotors.  I know, it sucks and it’s more expensive; but it’s not all bad.  This is the brake warning for newer BMWs equipped with iDrive (I’m starting to like iDrive), and it’s starting to cause some confusion . . .

Brake Pad warning from iDrive

This warning light will come on when one of the two brake pad sensors in your BMW has been activated.  The brake pad will wear down until the sensor is cut into by the rotor and the light or warning will appear.  There is no rotor sensor.  Brake rotors have a minimum thickness requirement specified by the manufacturer in order that the rotor can dissipate heat properly, maintain brake performance, and prevent warping of the rotor.  While performing a brake job on a BMW, the technician should measure this thickness and proceed accordingly.  I’d say that 95% of the time the brake rotor is either at or below the minimum thickness requirement and will need to be replaced.

Measure the Brake Rotor

In the case above the minimum thickness required is 20.4mm, and as you can see this rotor is just below at 20.11mm.  This rotor is now worth its weight in scrap iron.  Many have heard of ‘turning the rotor’ which is a process where the brake rotor surface is slightly shaved down to give it a renewed and clean surface.  If you have a Chevy or Toyota, you might be able to use your rotors 2 or 3 times before they need replacement, but not on your BMW.

BMW is very concerned about performance, the more weight you have out near the wheels, the less crisp and responsive the handling becomes and BMW wants to minimize that weight.  Brake Rotors are HEAVY.  BMW has been able to eliminate a decent amount of this weight by making the rotors a little thinner than other manufacturers, while maintaining incredible performance. The bad news is that you only get to use them once.  The good news is that this is just another example of BMW striving to have the best handling cars on the road.

So . . . when you get that phone call and you find out that you not only need brake pads, but rotors as well, it’s not that the shop is trying to pull one over on you — it’s just the nature of the BMW brake system.

Chris Keefer

Independent Motorcars

5836 Autoport Mall

San Diego CA 92121