Brake Rotor Deposit/Grooving

[timmo]

Does anyone know what would cause this? This is after 1 track day with HPS pads and Zimmermann rotors. I know, I know... HPS aren't meant to be track pads, but I haven't had any issues with them aside from going through pad material like crazy. I ran 4 track days with the first set I bought and the rotors had a bit of grooving, but nothing abnormal. Pad thickness is about equal inside and out, from what I can see without taking the caliper off.

Truth be told it might be my fault because I didn't bed the pads in when I replaced them - however I thought that was only necessary when switching pad compounds, and since I was replacing old HPS pads with new HPS pads, I wouldn't have to do so. Perhaps that would do it?

[racinghart]

Did this happen on all 4 corners? How do all of the pads look? I’ve seen this before with a sticking caliper causing brake drag and overheating the material.

[timmo]

Did this happen on all 4 corners? How do all of the pads look? I’ve seen this before with a sticking caliper causing brake drag and overheating the material.

I haven't gotten a chance to take stuff apart so I can't comment on the pads. This was the front LH corner, makes sense as it's a RH track - front RH corner was similar but not as bad. Rears are fine.

This is my rotor before this last track day, after 3 events with HPS pads:



Perhaps I should go for a casual drive, then check if the areas near the wheel bearing are hot. However I did street drive it and autox it quite a bit with the current pads before this outing and they seemed to be ok

[Slideways]

It looks like you need a dedicated track pad. Perhaps your driving skills are improving and you are carrying higher speeds and braking later than before.

[foolio]

It looks like you need a dedicated track pad. Perhaps your driving skills are improving and you are carrying higher speeds and braking later than before.

Came here to say this.

[timmo]

It looks like you need a dedicated track pad. Perhaps your driving skills are improving and you are carrying higher speeds and braking later than before.

Came here to say this.

This could be it - this was my first outing with coilovers, that plus cooler weather and better driving resulted in going from a 1:29.1 to a 1:25.9. Do you guys know if running different compounds front/rear messes with the brake bias too much? I'm thinking of keeping HPS in the rear (to keep costs down) since there's a ton of meat left on my 1st set, and getting DTC-60s on the front next year.

[Slideways]

This could be it - this was my first outing with coilovers, that plus cooler weather and better driving resulted in going from a 1:29.1 to a 1:25.9. Do you guys know if running different compounds front/rear messes with the brake bias too much? I'm thinking of keeping HPS in the rear (to keep costs down) since there's a ton of meat left on my 1st set, and getting DTC-60s on the front next year.

It could. According to this chart, the DTC-60 and HPS have a very different coefficient of friction and temp operating window:

[foolio]

This could be it - this was my first outing with coilovers, that plus cooler weather and better driving resulted in going from a 1:29.1 to a 1:25.9. Do you guys know if running different compounds front/rear messes with the brake bias too much? I'm thinking of keeping HPS in the rear (to keep costs down) since there's a ton of meat left on my 1st set, and getting DTC-60s on the front next year.

Using a pad in the rear that is not made for aggressive braking might be a false sense of economy. An improper pad can actually generate more heat and be worse on rotor wear. As you get faster, the correct pad will probably be cheaper in the long run. The excess heat and rotor wear will result in more frequent placement of your rotors and perhaps even other components like your wheel bearings if you are really overheating the rear end.

[Estoril]

The pad compound smearing looks like the pad temperature exceeded it's MOT. Which is not hard to believe with the HPS.

Run same pad compound front and rear - and I strongly recommend against using HPS on a track.

[Obioban]

As everyone has said, you've overheated your pads.

Time for track pads-- front and rear.

[timmo]

Thanks all. I will be looking into Ferodo DS2500 or DTC-60s from FCP

[r4dr]

DS2500 are barely track pads IMO. Not sure what tires you're running but I'd expect even 200TW tires to give them a workout. I've ran their equivalent on a GT350 with Super Sports and while they don't fade completely, they do lose a fair bit of bite and disappear before your eyes.

But they don't smear so I guess you'll have that going for you?

[timmo]

DS2500 are barely track pads IMO. Not sure what tires you're running but I'd expect even 200TW tires to give them a workout. I've ran their equivalent on a GT350 with Super Sports and while they don't fade completely, they do lose a fair bit of bite and disappear before your eyes.

But they don't smear so I guess you'll have that going for you?

Yeah, some of the reading I've done online concurs with what you say. I'm running RS4s.

Thing is I was hoping to run 1 pad for street driving (only spring/summer/early fall) and track, since my front caliper carrier slide pin threads are stripped and repaired with helicoil, and sometimes when I remove the slide pins, a helicoil or two may come with them. And since they're M9 thread, they're hard to come across. But really I just have to get off my lazy ass and source cheap used caliper carriers as replacements

[Obioban]

One pad for street and track isn’t a thing.

[Apex_80]

I look at it this way - you can run a track pad on the street but it will be annoying (loud and not as responsive) and also potentially hard on rotors. On the other hand you definitely can't run a street pad on the track as its a safety issue. With your replacements being free from FCP I don't see rotor life being a problem.