Blue Rotor Rings

[Stang70Fastback]

Looking for some feedback from more experienced folks than myself on this subject. This is my first year pushing a car "hard" on a regular basis (autocross) and I've encountered something for the first time that I don't know too much about. (I should clarify that I autocrossed last year too, but on a stock car, including the stock tires. This year I'm on RE71Rs.)

What you see here are photos of my front rotors taken after several autocross runs (each several minutes apart.) The blue ring is what I want to draw your attention to, as it indicates two things:

1. It's blue. I know this is obviously heat-related, but I'm curious if this is an indication of any "issue" or not? I know you can turn your rotors blue during bed-in, and that the blue color goes away as they cool (which it did here too.) I'm just curious if it's bad to repeatedly heat-cycle the rotors like that. I hadn't noticed it before, but it probably happens at every autocross. Not sure if it happens after each specific run, or just towards the end of each heat.

2. Only the inner 3/4 of the rotors are blue. This suggest uneven pad wear. Perhaps it's normal, since the brakes only have inboard cylinders, and that's just how the pressure distributes itself on the outer side of the rotors.
Basically, is there any reason to be concerned here, or is this just par for the course, and nothing to really worry much about? Google seems to give me answers ranging from "it's normal" to "your rotors will explode if you look at them funny."

Calipers: Stock
Rotors: Stock
Pads: Hawk 5.0

[radroach]

take the hawk pads out and show us the wear on them

[cjd]

Is that what happens when you take them out to race, but it turns out it was only an AutoX and they got excited for no reason?

[Tcoat]

Blueing from heat is fine when tracking the car. You know exactly what is happening to cause it. Blueing from heat on a street driven car (I mean a car driven normally) is a huge sign of an issue since you should not be braking hard or long enough to build up that much heat in your rotors. Also a bigger issue if only one is doing it of course. In the street case it isn't that the rotors are blue that is the problem it is what the hell is causing it. I think it is the "normal" use example where you read "They will blow up" since it keeps happening all the time until you fix the issue causing it.

Surface bluing of the rotors can be expected during track events and isn't hurting a thing. If you heat them up to the point that they warp or crack then you have an issue but you will likely have fade issues well before you ever hit that point. The reason that the outer edges don't blue is simple physics really. The outer portion is more open to the air and therefore remains slightly cooler even under heavy use. It only takes a few degrees difference for the more central sections to blue and the outer sections not too. Notice that the blue gets darker as it gets closer to the hat? There is more heat retention and build up as you get less airflow and more material.

All in all nothing to worry about but if you keep tracking a lot you may want to consider getting the ducted vents that go where the fog lights would. Not a huge improvement but they do move a bit more air across the rotors.

[JRitt]

The blue is pad material on your discs. It's definitely not an issue at all. Quite the opposite in fact. It's just the first time you've ever had your brakes bedded-in on your car! Check out our vids on Bedding and swapping pads. You can see me scrape that color/material off my discs, and add more from a different set of pads:

[ame="https://www.youtube.com/watch?v=pdPX6rzuINc"]How to bed-in brake pads[/ame]

[ame="https://www.youtube.com/watch?v=ONpSpWcy0V0"]How to swap between street and track pads[/ame]

Enjoy.

[renfield90]

Yep, my Hawk HP+ do the same thing. As everyone else has said, it's normal.