balbs

I heard that if you see a warning message on the iDrive regarding changing the brake pads, the pads were low enough that it shorts or cuts the sensors to set the message which in turn would need to be changed as well. On the iDrive, it shows that I have 4000 miles left on the front brake pads. When should I change the pads so that I won't have to change the sensor as well?

Thanks,

Balbs

5FOUR5

Idrive is a mileage based estimate, it is certainly just that as you have recently found out first hand. As driving conditions vary, the first telltale sign that pads might be nearing the end of service life, is the lip on the brake rotors BUT don't solely count on that symptom as I have seen pads nearing the end but rotors displayed a minimal amount of lip. An competent dealer / indy should be looking out and recommending such services if required. If you're doing all your maintenance by yourself, the only best way to tell is for you to take your wheels off and to measure the inside and outside pads with a gauge and spec it. The sensors are on the rear passenger and front driven wheel wells. You can pm me for further assistance / inquiries as I might be local to you.

fnc

Brake pad CBS data is not only mileage based. It adaptive, based on many inputs. One of which is the brake pad wear sensor. The sensor is two stage. If it is worn at all, replace it. I am going to try to find some info on it (that I have read before).

5FOUR5

While the pads cbs data is adaptive, its is still AT BEST a guess as the brake pad sensors have NOTHING to do with the service life indicators / interval that you see from the idrive. The sole data input for this function is monitored through the abs speed sensor and processed through the dsc module. The module then calculates brake modulation from the point it was activated - when you release, and take into account your current speeds. THAT IS ALL it calculates. It is a numerical calculation. While this is bmw's innovative way to monitor the braking systems, I will say it is much more advanced from previous methods, but it is by no means accurate as it doesn't take into account rotor and pad materials. The brake sensor that you find is a 1 wire ciruit that is insulated, and uses the rotor as a ground. Its ONLY funtion is to activate the brake service on your dash when the insulated wire is exposed to to ground (rotor). So in conclusion, the only thing adaptive about bmw's braking cbs is that it calculates brake modulation to determine service life, which STILL has no corralation with the actual condition of the pads or rotors. Information is information, the more the better when performing a diagnosis, but at the end of the day, the best way to check the conditions of your pads and rotors is still to take off the wheels to check the pad thickness with a gauge, and rotors for warpage and excessive wear.

JerseyGeorge

When you change the pads the sensors need to be changed also! The sensors are only needed on one wheel in the front and the back.

balbs

So I just noticed that the iDrive is estimating that I have 2800 miles left on the front brakes. I also recently noticed that it's starting to squeal like a baby banshee at low speeds. Is it time to change them? Should I wait for the iDrive to tell me? Is there a warning when it gets close to the final count down?

Hmmm....4000 - 2800 = 1200. I actually probably drove about 900 miles since the beginning of this thread. I do drive alot of city driving.

Balbs