Rotors

[M5Rick]

Original F/R discs at nearly 40k and looking good with just a little wear, should be good to 60k with brake pads at 8 and 6mm rear respectively.

[rockyfeller]

Looking at them visually won't tell you much. You need to measure the thickness with a digital caliper or something similar. It doesn't take even 2mm for your rotors to be out of spec, so it's wise just to check it out. The inner side tends to wear out slightly more than the outer, just keep in mind.

One sign to look out for is whether you have a lip on the outer edge. It's not necessarily a rule, but a good sign that the rotors have worn down quite a bit. No substitute to measuring them.

I just pulled my wheels and checked this out just yesterday on my car. My OEM pads have plenty of life but I wanted to change them out to Powerstops because they are low dusting. The dust and squeal are driving me nuts! Come to find out ALL my rotors are all BELOW spec!! 50k on the clock and I'm sure they're original. Pads were all changed 1x under the maintenance plan, but not the rotors. So at this point I realized it's better to do the pads and rotors all in one go so they wear in as they should. More money than I wanted to spend, but what u gonna do.

So I say pull out the measuring caliper and check it out so you know for sure.

[rockyfeller]

2 coin method works well. Try it out!

[M5Rick]

Originally Posted by rockyfeller

Looking at them visually won't tell you much. You need to measure the thickness with a digital caliper or something similar. It doesn't take even 2mm for your rotors to be out of spec, so it's wise just to check it out. The inner side tends to wear out slightly more than the outer, just keep in mind.

One sign to look out for is whether you have a lip on the outer edge. It's not necessarily a rule, but a good sign that the rotors have worn down quite a bit. No substitute to measuring them.

I just pulled my wheels and checked this out just yesterday on my car. My OEM pads have plenty of life but I wanted to change them out to Powerstops because they are low dusting. The dust and squeal are driving me nuts! Come to find out ALL my rotors are all BELOW spec!! 50k on the clock and I'm sure they're original. Pads were all changed 1x under the maintenance plan, but not the rotors. So at this point I realized it's better to do the pads and rotors all in one go so they wear in as they should. More money than I wanted to spend, but what u gonna do.

So I say pull out the measuring caliper and check it out so you know for sure.

Funnily enough my brakes don't squeal, BMW check the disc thickness each year and said it's fine even suggesting I don't use them hard enough!
I already bought some OE TRW pads f and b for future replacement but these pads seem to last for ever.

[eonianaerial]

It looks to wear well, thickness of the rotors aside. Mine does not squeal too or maybe im not using them hard enough to hear it.

[SpeedProtocol]

I see a lip, you dont have much left.

[rockyfeller]

A lip doesn't 100% always mean you're below spec but in most cases you probably are.

I'm very very light on the brakes. The dealer also told me for the longest time I was within spec. They even changed my rear pads under free maintenance but wouldn't change the rotors because they said they are well within spec. They said "corporate" measure the cores and they would get in trouble. Yea, ok sure. Now my plan has expired. I can bet anything that if I brought it in now, they would say my rotors are below spec. Lol. You wouldn't expect the stealer to play these games?

Your eyes can deceive you. Why trust anyone else either? Measure and see for yourself, then believe. Numbers don't lie.

[M5Rick]

Should last another 20k before discs get to minimum thickness.

[SpeedProtocol]

The discs only have 1.6mm of tolerance. If they have a lip they probably ARE at minimum thickness. Mine only made it 30k total before hitting minimum tolerance. These pads outlast the rotors. 20k more miles might be wishful thinking, just saying.

[M5Rick]

From what I hear it's rear discs that wear out first because of the traction brake actuation but I'm happy with my disc wear. When the pads are up then I'll check the disc thickness again.

[SpeedProtocol]

Id be happy if i had made it to 40k too.

[M5Rick]

Originally Posted by Droner

The discs only have 1.6mm of tolerance. If they have a lip they probably ARE at minimum thickness. Mine only made it 30k total before hitting minimum tolerance. These pads outlast the rotors. 20k more miles might be wishful thinking, just saying.

Who told you discs have 1.6 mm tolerance...so what's that it's 0.8mm worn each side and they need replacing? I don't think so

[SpeedProtocol]

They start at 36mm brand new and wear down to 34.4mm.... .That is 1.6mm total. This is what I am trying to tell you about the lip meaning they are almost done but you don't seem to want to listen.

[M5Rick]

Originally Posted by Droner

They start at 36mm brand new and wear down to 34.4mm.... .That is 1.6mm total. This is what I am trying to tell you about the lip meaning they are almost done but you don't seem to want to listen.

I'm listening good and just saying a little bit of lipping does not impair braking efficiency. I maxed my M recently (155 mph limited) then braked hard and soft with no vibration, buzzing or pulling with the s/belts pulling me back lol you are just wasting your money by replacing before time, these discs last much beyond 40k so long as it's not race track braking a lot of the time.
You drive in Texas so sand may expedite your wear?

[SpeedProtocol]

Sand? lol. Maybe the extreme heat might play a factor. I notice a big difference in the car being shittier all around in the summer. I was right at 34mm with a lip when I replaced mine. They were starting to vibrate. I think this floating rotor design deforms the discs easily with heat when they wear down thinner. And the caliper pots dont like to stick out that far if the pads are thin as well.

If yours are still good then they are still good, just saying there isnt much tolerance for wear on these rotors.

[M5_Raz]

It's probably the heat, Texas gets real hot, even worse than California. I found that when driving very normally on the street I barely use the brakes. The dct really stops the car much more than a regular auto.