Quote:
|
Originally Posted by HighlandPete
Interesting that his subject has been raised, as I have issue with the CBS estimate for my rear brake pads.
I'm due for a service next week and will be raising what is adrift with my car's figure. I'm at 25,500 miles and CBS is showing 7,000 miles to rear pad replacement. I've measured the pad thickness and it is ~8mm. I understand new pad thickness is ~12.7mm, therefore for 25,000 miles pads are worn down about 5mm. I estimate I should get at least another 20,000 miles before pads are down to 3 - 3.5mm.
I'm not a heavy brake user in my conditions, according to the service record rear pads were reported to be 9mm at <12,000 miles. So according to my estimate they have worn less than 2mm in about 14,000 miles.
I never had the car until 6,000 miles, so I'm guessing the BMW HQ driver was braking much more when the car was 'collecting' the initial data for estimating pad wear. But hasn't re-estimated the wear rate since that time. The front pads are still in good fettle with 46,000 miles on the CBS countdown.
I'm sure my garage will simply reset the CBS for the pads, (once they have checked them) as I don't want warnings way before I know the pads are worn down to replacement thickness.
BTW, my last BMW (E91 330d) I had new, at 52,000 miles was still on original pads with the rear pads (6mm) still indicating much more life.
HighlandPete
|
Pete, yes, the shop will measure and if there is too much meat left, they actually have an algorithm that recomputes the estimated number of miles remaining. They will reset the warning and by re-entering the estimated number of miles remaining and you'll be on your way.
My speculative theory is that there exists logic that takes into account the number of brake actuations made by the driver and the number of actuations made by the ABS system.
This is outside of the sensor data.
Well, i think BMW has a safety counter that tries to act as another source in determining wear.
This safety counter threshold is out of whack and this causes iDrive to have the wrong number of remaining miles.
BMW engineers simply underestimated the real life number of short brake actuations by man and ABS.
And I believe this led to the discrepancy.