Quote:
Originally Posted by rh71
there's a sensor on the brakes - for what exactly I don't remember, but logic tells me since idrive shows pad wear and not rotor wear, I'll go with that one. Obviously it's not exact since it goes in maybe 1k increments.
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On the E53, before iDrive, the sensor on the brake pad was a simple wire that rubbed through, and opened the circuit. That triggered the light, informing the driver that it was time to change the pads.
On the E70, pad life is calculated from 60,000 km (from memory) based on how many times and how hard the brakes are applied. It is an algorithm that I don't think is particularly accurate, as I tracked it on my E60 watching how it counted down (it didn't, but I had non-OE pads from new and so it likely couldn't figure out how they were wearing). The pad sensor on the E70 has two thin wires embedded at two pad thicknesses; when the first wire rubs through the resistance changes and it knows the thickness of the pad that is remaining. The computer uses that to correct the algorithm, giving a more accurate "distance to change" figure on the dash. It is why the life-remaining indicator jumps at a certain point. Then when the second wire rubs through, the system functions just like the E53, and lights up a warning saying to change the pads.
It is all described in detail in the E70 service training materials posted under Online References in the top menu bar.
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2007 X3 3.0si, 6 MT, Premium, White
Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue
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