[itshere]

As the title suggests., how accurate are the alerts to replace brake pads/rotors. Shows that it should be replaced in 1000km for me - still runs smooth, no noise, no complaints. I’d imagine if I got to a local mechanic they would tell me to ignore it while BMW dealership will want to replace the pads/rotors.

Indicator says rears need to be replaced. Will attach a picture of the rears and fronts.

Pic 1-3 are rear
4-5 fronts.

Edit: what about rotors? Should that be changed with the pads?

[AvGeek]

Those actually look pretty damn worn to me. You really don't want to let the pad material go ALL the way down. There should be an indicator in the middle that is probably almost gone, so I'd say at least the rears need to be replaced now rather than later and the fronts soon too.

[Traxion]

Not gonna bother guessing which pics are which position but the pads in picture 2 and 3 are definitely low and need to be replaced. The sensors get nicked when pad thickness gets under a certain millimeter so it's very accurate.

[mmm50i]

Originally Posted by Traxion

Not gonna bother guessing which pics are which position but the pads in picture 2 and 3 are definitely low and need to be replaced. The sensors get nicked when pad thickness gets under a certain millimeter so it's very accurate.

I agree with this. Pictures 2 and 3 are really thin!

[itshere]

What about rotors? Should that be changed with the pads?

[eelnoraa]

I agree #2 and #3 are thin, they should be replaced soon if not now.

Rotor looks OK to me. A brake job at BWM dealer will replace rotor regardless because dealer won't do resurface. If you are doing brake job else where, the capability of getting brake rotor resurface properly is lost, so it is a hit or miss. If resurface is done correctly, all will be good. Otherwise, you will have vibration or noise ... other artifact, which may require rotors to be taken off for another resurface or replacement. If you are doing DIY, maybe give it a try. If you are paying labor, I think just get rotor replaced as well. In a grand scheme, labor cost is the large part.

[LuckyBrand]

I replaced pads and rotors last fall on our x5 after the sensor tripped after over 80 thousand miles of use. And yes they were accurate and needed replace. I trust the sensors after that.

As far as rotors. For me I always replace them. Unless I'm replacing pads every 40 thousand. But I usually get 70 to 80 thousand miles easily out of brakes so I figure I'll do the whole job once and most likely won't ever have to again. I also do my own labor so that saves a ton of money.

[jad03060]

There’s a minimum thickness needed on the rotors. After you resurface them, there MIGHT not be enough left before the new pads wear out. A lot of it is labor…new rotors and pads is certainly easier, except maybe on your pocketbook, at least initially.

[slilley]

I typically replace the rotors every-other pad change. By that time, the rotors are usually down to their minimum thickness.

In my experience, the BMW wear sensors fire an alert when there are still safely 1-2K miles of pad material on the front, and 3-4K miles of pad material on the rear (assuming they'd be replaced with 1mm remaining).

One word of caution about those pictures above: usually the inside pad wears faster than the outside pad, so I usually assume the inside pad is 1mm lower than the outside pad that I can see.

[eelnoraa]

Originally Posted by slilley

I typically replace the rotors every-other pad change. By that time, the rotors are usually down to their minimum thickness.

In my experience, the BMW wear sensors fire an alert when there are still safely 1-2K miles of pad material on the front, and 3-4K miles of pad material on the rear (assuming they'd be replaced with 1mm remaining).

One word of caution about those pictures above: usually the inside pad wears faster than the outside pad, so I usually assume the inside pad is 1mm lower than the outside pad that I can see.

BMW wear sensor is not related to mileage at all. The sensor is nothing more a piece of metal conductor, about 2mm thick. When pad is worn down to ~2mm or so, the rotor will start to wear the sensor. Once the sensor is wore broken, it create an open circuit triggering warming. Simple as that.

And absolutely not true that inside pad wear faster. This really mean the your caliber pins may need some maintenance or needs to be replaced..

[slilley]

Originally Posted by eelnoraa

BMW wear sensor is not related to mileage at all. The sensor is nothing more a piece of metal conductor, about 2mm thick. When pad is worn down to ~2mm or so, the rotor will start to wear the sensor. Once the sensor is wore broken, it create an open circuit triggering warming. Simple as that.

And absolutely not true that inside pad wear faster. This really mean the your caliber pins may need some maintenance or needs to be replaced..

Yes, you are technically correct - the sensor is not related to mileage at all. The mileages I quotes are based on the wear of the pads, i.e. when the circuit becomes open because the sensor has rubbed away due to contact with the rotor. This happens long before the pad with the sensor is at 1-2mm thickness. It happens when there are still 3-4mm of pad material left. THAT pad thickness is what I'm talking about when I say there are X thousand miles remaining. You need to change the pads before the pad material is completely gone and the backing plate is making contact with the rotor. If you change the pads before you are down to 1-2mm, you are changing them before it's truly necessary. But it's always best to do it early than to do it late, as you don't want to run the risk of running out of pad friction material.

Most pads start at about 10mm thickness when new. As you drive, you slowly wear away the pad material - that's (mostly) what the brake dust is. (Some of it is rotor wear too.) I actually measure my pad thickness during regular services with a brake pad thickness tool (available on Amazon; I recommend the metal version from Steelman p/n 97844). So, if I know that (for example) I use 1mm of pad material for every 2.5K miles I drive, and the sensor goes off with 3mm of pad material left, I know I can comfortably drive another 2.5K miles before I'm at 2mm remaining. That's what I meant when I quoted those mileages. Of course, I only have 17K on the X5, so the wear I quoted is related to my daughter's F48 X1 and our previous F25 X3.

My second comment about inside pads wearing faster is absolutely true, however. Yes, the difference between inside and outside pad wear should be minimal, but it will still often be measurable. Usually it's less than 0.5mm - and can be as small as 0.1mm. But a floating caliper will always wear the pads out on the piston side a smidge faster. I think the brake pad sensors on BMW's are all on the inside pad for this reason. Porsche puts their brake pad sensors on BOTH pads. But you are correct that if you see drastically different pad wear on the inner and outer pads, you've got a problem. In the hundreds (thousands?) of brake jobs I've done on my cars over the years, that's something I've only seen once - and it was actually caused by a failing wheel bearing (on an Infiniti, not on a BMW!).

[davchr]

The only way to know if the rotors REALLY know if they need replacement is to measure them. Anybody, that knows what they are doing, will measure runout and minimum thickness and determine if they can be safely machined. This is my first BMW. In the many other cars I have owned I have never needed to change rotors with the first pad change.

[Alan l.]

Your pads are shot and so are your rotors based on the sizable lip formed at the edge. They aren't expensive if you order oem through online retailers. You might want to order new front and rear wear sensors while you are at it.

I changed my X5M rotors at around 30K based on the min thickness measurement I read and the lip at the end of my rotors weren't even as bad as yours.

[eelnoraa]

Originally Posted by slilley

Yes, you are technically correct - the sensor is not related to mileage at all. The mileages I quotes are based on the wear of the pads, i.e. when the circuit becomes open because the sensor has rubbed away due to contact with the rotor. This happens long before the pad with the sensor is at 1-2mm thickness. It happens when there are still 3-4mm of pad material left. THAT pad thickness is what I'm talking about when I say there are X thousand miles remaining. You need to change the pads before the pad material is completely gone and the backing plate is making contact with the rotor. If you change the pads before you are down to 1-2mm, you are changing them before it's truly necessary. But it's always best to do it early than to do it late, as you don't want to run the risk of running out of pad friction material.

Most pads start at about 10mm thickness when new. As you drive, you slowly wear away the pad material - that's (mostly) what the brake dust is. (Some of it is rotor wear too.) I actually measure my pad thickness during regular services with a brake pad thickness tool (available on Amazon; I recommend the metal version from Steelman p/n 97844). So, if I know that (for example) I use 1mm of pad material for every 2.5K miles I drive, and the sensor goes off with 3mm of pad material left, I know I can comfortably drive another 2.5K miles before I'm at 2mm remaining. That's what I meant when I quoted those mileages. Of course, I only have 17K on the X5, so the wear I quoted is related to my daughter's F48 X1 and our previous F25 X3.

My second comment about inside pads wearing faster is absolutely true, however. Yes, the difference between inside and outside pad wear should be minimal, but it will still often be measurable. Usually it's less than 0.5mm - and can be as small as 0.1mm. But a floating caliper will always wear the pads out on the piston side a smidge faster. I think the brake pad sensors on BMW's are all on the inside pad for this reason. Porsche puts their brake pad sensors on BOTH pads. But you are correct that if you see drastically different pad wear on the inner and outer pads, you've got a problem. In the hundreds (thousands?) of brake jobs I've done on my cars over the years, that's something I've only seen once - and it was actually caused by a failing wheel bearing (on an Infiniti, not on a BMW!).

Just want to be clear, the mileage you quote is based on your very personal usage, right? Another person's driving habit can and will be significantly different. In one example of my own, I can wear out a set of front in 8K for some usage. The same car, the 2nd set of OEM pad, get me to 90+K and sensor isn't even tripped. The only difference for my 2nd set was, I swapped pads for track events, but the accumulated mileage for track event cannot be more than 500 miles.

As to pad wear fast on the piston side, I am not sure we are looking at G05 properly. The fronts are multi-piston calipers. Pistons are on both sides, as in picture 4 and 5. So which side wear faster?

Sensor on the inside pad is NOT because inside wear faster at all. Going by this logic, BMW only put sensor on front left and rear right, does it mean front left is wear faster than front right?? To me, putting sensor on the inside is a practical choice because you can see the outside pad and get a good idea of the wear condition. The inner, we typically have to guess. With sensor on the inner, it gives a indication of the non visible pads

[slilley]

Originally Posted by eelnoraa

Just want to be clear, the mileage you quote is based on your very personal usage, right?

As to pad wear fast on the piston side, I am not sure we are looking at G05 properly. The fronts are multi-piston calipers. Pistons are on both sides, as in picture 4 and 5. So which side wear faster?

First question: YES! It's based on my personal usage and a mix of city and highway driving. More importantly, the mileage I quoted is based on previous BMWs - I've only got 17K on the X5, so I've not even measured the pad thickness yet. I'll look at them for the first time when I do a 20K mile tire rotation.

Going back to the OP question: how accurate are the alerts to replace pads? For 99% of drivers, they are SUPER-CONSERVATIVE. That's the point I'm trying to make. When the light goes on, probably 99% of drivers have at least 1K miles before they are out of pad, and in my experience with other BMWs (and Mini's) there is always more like 2,500+ miles before the pad material is gone. BMW gives us LOTS of warning, which means that many of us can drive around for months with the brake warning light on. But am I saying that's a good idea? No.

As to your second point: I didn't realize the X5 front brakes had multi-piston calipers! <Doh!> So at least for the fronts, you are correct that both inner and outer pads should wear at the same rate.

[jad03060]

Bottom line, the brake wear sensors are telling you the thickness of the remaining pad when they first alert you…how you drive will affect how far you can travel with them at that thickness, so your actual mileage can vary significantly. Do a lot of mountain or city driving or towing or racing, and your remaining miles will be lower than with a more ‘normal’ driving picture.