Strange pattern on my brake discs

[georgesgiralt]

Hello,
I replaced the oil in my fork tubes. At this occasion I noticed a strange pattern on the brake discs. Both sides.
OEM discs with OEM brake pads.
What is causing this and should I care ?
Thanks in advance for your help.

[Bob_Roller]

It's caused by the holes in the rotor being in a straight line, a lot of aftermarket rotors have overlapping holes .

[georgesgiralt]

well, in more than 200 000 km with this bike, it is the first time I see the outer ring on disks.
Having the ridges undulated because of the disc holes I have seen, but not this.
It looks like only the outer part of the disk is used for braking and thus the wear.
Anyway, thanks for your answer.

[Kelvin]

That's the normal pattern for wearing, but the pronounced ridge at the rim probably indicates that the disk has worn beyond spec and should be replaced. Replacement disks come with carriers (the bowl that the disk is riveted to and which bolts to the wheel) and are expensive. It may be possible to replace just the disks and have them attached to the old carriers.

You need to replace the pads when you replace the disks, of course.

[georgesgiralt]

Well, those disks and pads are new. About less than 10 K  km...
And they where OEM (bought  NOS at a dealer's closure for less than a third of BMW price)

[skippyc]

That's a lot of wear for 10K. Do you do a lot of stop start riding?

[Bob_Roller]

Have you checked the thickness of the rotor near the hub and the outer part ??
I didn't have that kind of ridge at 78,000 miles, 130,000 km on my original rotors .
Have you removed the pads and see what kind of wear pattern you have ??

[georgesgiralt]

Will check ... And report. I was away for a couple of days.

[georgesgiralt]

So, I spent half of the afternoon in the shed. Very hot in there.
The rotor has no ridges I can sense with my nail. The ridges seems even enough to sense the same under the nail.
I cleaned the rotors with brake cleaner and most of the trace is gone (there is a small left).
I removed the pads. They were glazed and very brilliant. i used a nice file to make the dull and looking like they are new.
I cleaned the calipers in order for the pads to run free into them. And for good measure, I cleaned the retaining pins with green Scotch Brite.
Tomorrow I've to help my sister in law and will take the bike for a run to see how the brakes manage.
I've also tested the old voltage regulator (the Wherle metal can electronic which came with the bike and failed very long ago ... ) I repaired some weeks ago. I set it for the AGM battery I run on the bike per Snowbum's instructions.
So quite a busy afternoon !
Time for a shower and a beer !