[Kkuba]

Hi guys,

I'm getting a strange thing happening with my service intervals.

Car is an E82 135i MT 2008, with flip-screen iDrive.

When I bought the car a few years ago, it needed new front pads and rotors. I went and bought new pads and rotors and sensor direct from a BMW dealership.

The service interval was still over 5000km left according to the iDrive, but the change was required for RWC when I was transferring the car into my name.

Installed them, and soon after, I reset the interval using a diagnostics device (Autel brand), and was on my way.

I didn't think much of it, until about 20,000 km and a couple of years later, when the car was indicating a service due soon. Checking the iDrive, it was being triggered by the front brakes.

So, I thought maybe I had not finalised the reset the first time, and did it again. And didn't think about it.

Less than 10,000 km later, same thing again.

So this time, immediately after resetting it, I checked the remaining km according to iDrive, and it was only giving 10,000 km until the next service. I thought that was odd, but left it for further investigation later.

After driving it for a few days (less than 500 km), the service indicator appeared again. I checked the iDrive, and brakes were indicating 3600 km until service required.

Why is it doing this? As I mentioned earlier, all replacement parts were genuine.

Just looking through the wheel, the pads themselves appear to have around 8-9 mm of material left.

Is it possible I installed the sensor in the wrong position, and it is wearing down prematurely? I don't remember it being particularly easy to get wrong, but maybe this is a common problem?

Thanks in advance for your help guys. = )

[floydarogers]

I think you've confused the computer by resetting it.

Modern BMW brake sensors have two wires: one that is near the top and one at the bottom (of the pad's thickness).

The bottom one is just like all the older ones: when it is cut it means "change pads now!" because you're basically going to be metal-on-metal in a very short time.

The upper one wears through after a relatively brief time after it's installed. The computer uses that mileage (after install) to estimate a time when you will need them replaced. Your constant resets are confusing, as it can't estimate that mileage because the upper one is already worn through.

Or at least that's my guess.

[patents]

My guess is like floydarogers. It guesses how many miles the pads will last. Of course, pad life is highly dependent on driving habits. Two-stage sensors work like this: You reset it, it guesses the mileage. When the first sensor is worn and tripped (at 50% thickness is my guess), the computer adjusts its calculation since it now knows how many miles you got out of the first 50% of pad thickness.

I think what's happening is that the computer thinks that the brakes must be worn out at each reset. So it's estimating that each set of brake pads only lasts you a few 1000km.

It's not supposed to tell you that the brakes are actually due until the final sensor trips. The mileage is just an estimate. And the sensor is one-time use. Once it tripped (by a break in the wire), it's done. The computer just looks for that open circuit.

What did the idrive message actually say?

[Kkuba]

Thanks for the responses, BUT:

When I first changed the pads it did not update the service interval, so for a few weeks/months i was driving around with new pads and rotors (and sensor) with only 5,000km indicating until a change is required, that is the reason I did the manual reset (usingthe Autel) in the first place.

[bdhh]

option 2
Just cut & strip the wires, & join them together.
Throw the sensor in the garbage. thats what i did.
Its easy to look at the pads with a mirror, once a year.