2005 645ci brake service

[theg]

Hello all .
Im curious about my 2005 645ci brake wear monitoring and replacement of the servicable parts .
Firstly will some sort of warning display when the sensors detect worn pads or will It only show in the screen of the idrive as klms left before replacement .
If the last pad replacement mileage wasnt put in the computer will the displayed remaining klms be incorrect ?
My car is currently showing 2400klm left on rear pads but dont know how to interpret this as I dont know the cars history with pad replacement .
Ive recently also been advised the rotors and pads should be replaced together as standard practice on these cars not just pads only even if rotor thickness is still in the servicable range , can this be confirmed ?
Any help is greatly appreciated.
Thankyou to all .

[MarcoZandrini]

A dealer will likely want to replace both pads and rotors even if the rotors have plenty of “meat” on them. Personally, I change only the pads unless the rotor thickness is getting close to the minimum thickness. Btw, the minimum thickness number is stamped on the rotor hub. So, using a quality micrometer will tell you if the rotor needs to be replaced. A word of caution: do not buy inexpensive aftermarket rotors as they’ll warp in short order. Buy rotors from the dealer or buy Zimmerman rotors from a supplier. Zimmerman rotors are made in Germany and the company supplies rotors to BMW.

If the car’s computer wasn’t told that the pads were changed then I highly doubt if any miles remaining number will be accurate. A second word of caution: unless you drive your car at serious triple digits at the racetrack, buy replacement pads at the dealer or buy pads made by one of the brake pad suppliers to BMW. Factory pads are made by Textar or Jurid. Why? The pads are engineered to BMW’s specifications.

[bmwdirtracer]

There are two separate systems at work, to monitor your brake pad wear. Neither of them is perfect.

System 1 is an old-school wear sensor, which is plugged in to the left front inside pad, and another in the right rear inside pad. When either of these sensors contact the brake rotor, you will receive a warning light; perhaps a couple of them. The trouble with system 1 is that it really only monitors 2 brake pads - out of 8 total. Brake pads don't always wear identically.

System 2 is the CBS, or Condition Based Service system, which uses data from your car's computers to estimate when you need brake pads, or an oil change, or cabin air filters, or a brake flush. CBS has a couple of "imperfections". Firstly, it can be reset without doing the service....which some shops or used car dealers will do, so that you don't have a "service" light (picture of a car on a lift). Besides that, as I said, CBS is an ESTIMATE.

For example, I guarantee that I would wear out the brake pads LONG before the CBS thinks they're due. Conversely, if the car went to a generic (non-BMW) shop for its last brake job, they wouldn't have known to reset the CBS.

If you become familiar with what a good brake pad looks like, vs. one that's worn out, you can examine all 4 outside pads, and the rotors, by peeking through the wheels, in less than a minute. Certainly, I can't explain how to do this without both of us looking at the same car together, but once you've seen the technique, you can easily monitor your own brake wear. Although you should use a micrometer to measure rotor wear, IF there is a significant ridge on the outer edge of any rotor, the rotors on that axle need to be replaced. If there's no significant ridge, but the pads are worn out, I'll sometimes replace just the pads, if the owner is trying to be frugal.

On a 645, there's really no point in trying to be frugal. You own a car which cost probably $100,000 AUS new, so you should expect to spend ~$4000 a year in maintenance and repairs.

I highly recommend that you avoid generic repair shops, and take your car to a good BMW specialist shop, and try to learn to do the simpler jobs (like brakes) yourself. This car IS a maintenance monster though, like every flagship BMW and Mercedes.

And, by the way, I completely agree with Marco about using high quality original BMW pads and rotors, or the OEM (original equipment manufacturer) parts, from a quality BMW specialist supplier. If you go to a generic shop, you will get GARBAGE parts.