Hot spots on two piece rotors?

[Mad1186]

Hello! I’m sure someone has had this problem or someone similar, so i have a set of Girodisk 2-piece rotors and GLoc R16 pads up front, these were bedded in properly Ofcourse. I have done a couple track days and my two recent ones were at Road Atlanta *which the rotors looked great* and The Firm. After checking over the car once i got home they came out like this. Can someone explain to me why this could have happened? The face of the rotor looks like this but the back doesn’t. My rear rotors are fine and have GLoc R12 pads and they look nothing like this.

-Should i just sand down the rotors and restart the bedding process? -Try out different pads instead? -Should i check if the pistons on the caliper are sticking? Need some help please! I really hope i didn’t already trash these rotors and hopefully are savable.

*Dont mind the two missing studs, lugs seized on and i had to drill them out.*

 

[byronj]

I would check to see in the piston are sticking. Looking at the back of the pad, you can see there is a lot of heat in there. I brake late and hard and the only time my pads looked like that was when my piston stuck. I had CC rotors and it destroyed it.

 

[Mad1186]

I would check to see in the piston are sticking. Looking at the back of the pad, you can see there is a lot of heat in there. I brake late and hard and the only time my pads looked like that was when my piston stuck. I had CC rotors and it destroyed it.

I was thinking maybe to rebuild these also, i sometimes have brake problems on track and it is not very inspiring.

 

[Mad Hatter]

Do you have any cooling ducts?? Always a good idea! I have seen this sometimes when coming back from the track with slow city driving. The Glocs are a race pad so they can leave some funky residue on the way home when you get stuck in slow driving. The discs look fine and I would check what they look like right after a track session.

For example, RSL 29 Pagid pads would do this when they were too cold and they have a wider temp range then the Gloc R16's. I Do prefer the Gloc R18 pads to the 16's in any case.

 

[Mad1186]

Do you have any cooling ducts?? Always a good idea! I have seen this sometimes when coming back from the track with slow city driving. The Glocs are a race pad so they can leave some funky residue on the way home when you get stuck in slow driving. The discs look fine and I would check what they look like right after a track session.

For example, RSL 29 Pagid pads would do this when they were too cold and they have a wider temp range then the Gloc R16's. I Do prefer the Gloc R18 pads to the 16's in any case.

I have just the oem brake cooling ducts, but yeah maybe i should try another track day and see, The firm is pretty harsh on breaks and it was 100 plus degrees, maybe the heat really got to them?

 

[GAR944]

Do you have any cooling ducts?? Always a good idea! I have seen this sometimes when coming back from the track with slow city driving. The Glocs are a race pad so they can leave some funky residue on the way home when you get stuck in slow driving. The discs look fine and I would check what they look like right after a track session.

For example, RSL 29 Pagid pads would do this when they were too cold and they have a wider temp range then the Gloc R16's. I Do prefer the Gloc R18 pads to the 16's in any case.

Agree, RSL29's on a GT350 Rotor, when you work them really hard they smear material and its always around any surface opening.


My friends 370Z with track pads, looks re-markedly similar. The surface engravings i believe effect how much material seems to collect. My 944 would do the same.


As for them doing it on the outer surface and not the inner, i'm guessing it may just be the outers get a higher surface temperature from not getting wheel well air pushed over them.
As i've mentioned to others, big heavy car, especially in full road trim, capable of good speed out of the box needs as much brake and cooling as you can throw at it. Ford gave us the bare minimum as a starting point.
You may find as my friend did, the brakes pulse a little as they pass over the material build up. I just gave them a light scuff with a DA sander to get them consistent again. He did end up changing rotors and with a shallow straight line groove, the material build up was way less. Nothing scientific, but so far.

As @Mad Hatter mentioned, brake duct / deflectors to throw as much air at them as possible. Brakes aren't cheap but some ingenuity and/or internet search will give you plenty of options.

And copper grease on the threads will stop your nuts from seizing. Especially on track cars where the heat and constant on/off of wheels with impacts can give the threads a hard time.