Why are my rotors glazed only on the outside

This is what my two front rotors look like after a track event last week end. Any conclusions to draw? 

What is the physical explanation for the glazing to be only on the outside? 

Is it the same on both sides of the car, and on inner and outer faces of the rotor?

Is it glazing or colour change from heat? Is that picture right off the track or are we looking at rotors you've used driving home from the event? I know my rotors look a bit blue after a day at the track and that surface colour disappears after some more "normal" use.

If I had to guess it looks like an E36, possibly M3? What pads are you running and what's the car setup?

GameboyRMH said:

Is it the same on both sides of the car, and on inner and outer faces of the rotor?

It's the same on both sides of the car, and I've yet to look at the other side of the rotor. Just had a quick look today, I will report back when I get a chance to see the other side. 

adam525i said:

Is it glazing or colour change from heat? Is that picture right off the track or are we looking at rotors you've used driving home from the event? I know my rotors look a bit blue after a day at the track and that surface colour disappears after some more "normal" use.

If I had to guess it looks like an E36, possibly M3? What pads are you running and what's the car setup?

"Is it glazing or colour change from heat":  I am not sure how to distinguish the two. This picture is of the rotor I used on the track, and to drive back home (100mi).  You are close, it's an E46 M3 and I was running EBC blustuff pads on Fremax rotors ($75 rotors sold by bimmerworld). 

"what's the car setup" : It's a car I'm slowly building with a track focus, but still very streetable.  Ohlins R&T coilovers with Vorschlag camber plates and a track alignment, Hotchkis swaybar, stiffer bushings all around. I also got Falken Azenis RT660s. 

Ah, E46 M3, hard to beat, very nice.

Also nice to see the BMW CCA badge in the grill and numbers from one of their schools on the windshield. I just became an instructor with the Trillium Chapter this year. What track were you at and which chapter?

So I guess the next question is if you were experiencing any braking issues such as fade or pulsing as things got hot or sessions went on, if no I wouldn't worry too much about that colour on the rotors. It wouldn't surprise me if they were more evenly that colour straight off the track and now that you've driven them home it's starting to get worn off.

If you were experiencing some fade or pulsing from pad transfer (indicating pads are getting too hot and outside of their operating zone) then it might be time to get a track specific pad rather than one marketed towards street and track. I personally run the Powerstop Track Day Spec pad which are very affordable on Rockauto (don't forget the 5% discount code) on my E28 (happens to be the same pads your car would take believe it or not). Like any track pad they aren't great when cold and tend to eat rotors at those colder, street temps, they also dust really bad but I haven't had noise issues. On track they come into their own with a little heat in them, I've never experienced any fade whatsoever even pushing the car at some brake intensive tracks, it is a bit lighter car with a bit less power than you though. Pads are where the braking performance comes from so the rotors you are running should be just fine.

That's looks like normal pad transfer, partially removed from driving home.

When a fixed rotor gets hot, it forms a bell shape...which wears both the pad and rotor in a wedge shape.  When it cools to street driving levels, the contact area is the opposite. 

Street driving removes the transfer layer but only where the most pressure is being applied.  I see this all the time on cars I drive to/from the track...but never on the trailer queens.