CO_VaporGT_09

What do y'all make of this?

These are symmetric, L & R, inner and outer surface, after 4 track days (2 weekends), four 20 min sessions each day, speeds to 120mph.

Roush TrakPak rotors, EBC Bluestuff pads, traction control off whenever on track. Front are StopTech/Saleen 4pots.

Normal? Sign of a problem?

07S197

Heat, it looks like the rotor overheated and those are "hot spots". That is very similar to what I see at work on an overheated flywheel.

yugoboss

Looks like hot spots to me.

houtex

Weird, I can't see if those are vented or not. I'm guessing yes, which would explain the pattern.

Kinda pretty...

/and time to replace, I think.

CO_VaporGT_09

Quite right, houtex, I saw your reply and immediately realized it -- they do exactly match the vents/slots or whatever on the inside of the rotor.
Thanks for all the quick replies!

You sure I have to replace the rotors already? They're not that old, have plenty of thickness left. No visible cracking, either.

So, now the problem is identified, what's the solution? I've not had any particular braking problems at the track once I moved to the Bluestuff (and going to Hawk DTCs next year when I start time trialing).

Have the rear dust shields removed already; would a better wheel design (I'm using GT500 takeoffs on the track) improve airflow? I'm not sure how ducting would work in the rear, other than those Agent 47 quarter window NACA ducts:

http://www.cjponyparts.com/AGENT+47+...-2009/p/QWL18/



But this will still be a street car, those aren't very street car friendly.

slidejob

Get a brake temp kit.

http://www.apracing.com/info/info.as...emperatures_44

07S197

Often we resurface the flywheels at work without any issue. I don't know if that would work on rotors or if I would even want to try that for safety reasons. I don't know that I would take the chance.

Talk to others you track with to see what they are running, maybe it is time for a rear brake upgrade. Repetitive hard braking at 120mph is going to kill just about any rotor that size. Even with a duct kit idk if you will keep them cool enough.

Are you running stock GT500 pads up front? If so you may need to down grade those rear pads to match the fronts. Or even down grade them anyway just so they are not so aggressive.

CO_VaporGT_09

There's no pulsing/judder on braking at this point, so they're not 'warped', which is actually uneven pad deposition. But it's not the case here, the metal itself is actually discolored so as y'all said it's that it's been repetitively heat cycled. So I don't think resurfacing or turning the rotors would have an impact.

The pads are the same all around, EBC Bluestuff which is a high-temp track pad. Probably why the braking is still doing okay despite the heat.

There aren't any real good rear brake upgrade options, either, there's the 13" Steeda rotor kit that requires pulling the axles, and moves the stock caliper a bit further out, but several more experienced track people have said it changes the balance of the braking system too much. There's nothing else that's really 'track proven' -- all the FR500C, S, etc race cars use the stock calipers (sometimes due to class rules, but generally they're not a limitation).

The thing is my car is way way heavy, I'm guessing 3800lbs+ with me in it (gonna pull out the 12" subs and two big-*** amps I installed before realizing I was getting so much into the track driving). So hopefully a few hundred pounds lighter (looking at lighter weight wheels, too) might help.

I'm gonna post over in the road race section and see what they say as well.

07S197

Maybe you need to go back to a less aggressive pad. Those pads my build too much heat to quick for the rotors to take. Talk to EBC, do they recommended a specific rotor for those pads?

CO_VaporGT_09

They actually say they're the first ever "combined street/track pad" that's suitable for the street (which is BS of course, none of them ever can be -- they squeak and dust more than is reasonable, though better than Hawks).

I'm thinking maybe going with the DBA rotors, their vane pattern might create a better heating/cooling cycle.

http://youtu.be/8PzWFn6lGBs

But pricey, about $150 per rotor (the Roush ones were $200 for the pair).

The rear brake pads also wear very quickly, much faster than the fronts. The suggestions for the Hawk's (haven't switched to them yet as they're about twice the price) is DTC60 front, DTC70 rear, so following what you're saying of a less aggressive pad in the rear.

PTRocks

Have you removed your rear splash shields? That should be your next step if you haven't done it already.

CO_VaporGT_09

Yes, I did this year, though used these same rotors last summer without having done so, and maybe the faintest hint of this before, but it's now much more prominent (I'm getting faster and faster, and have stickier tires now, so driving harder, using the brakes more).

I've got ducts in the front, and switched to two piece StopTech rotors beginning of this year and they're working great, no unusual patterns (though they also have curved 'Aero' vanes instead of the straight radial ones that are typical).

07S197

I think thats it right there, I would call EBC and ask what rotors they recommend

Ronin38

Just as an FYI, a friend of mine took a slightly different approach. He does track days in a Dodge Magnum (4400 lbs!) and just treats the rotors as "consumables" like the pads. His front brakes are all top-line, but his rear brakes are still the SRT-models. He gets the stock rotors wherever he can find them the cheapest, and just replaces them more frequently. He's also found that the heavy rotors make a better "heat sink", and don't crack and fade during a track day or two. They rarely last more than 5 days of track time, then he just changes them.

Sabre

I could be wrong, but I thought it was DTC 70 on the fronts and DTC60 on the rear. I'm using the same rear Roush rotors that you have and Hawk HT10 on the rear...I've never had on mine, what your photo shows...my rear rotors look just like the fronts. I'm using the DBA 4000 series rotor on the front.

CO_VaporGT_09

You're right, I got it backwards, 70s on front, 60s on rear, or HT10s on the rear is the other good combo I've heard.

What kind of life do you get out of your rear Roush rotors (I think they're actually PowerStop brand, relabeled -- it's a StopTech company now, too)? I'm picking up some cheap blank ones like mentioned above $36/per at TireRack, and will just go through them quicker, see if there's any difference.

Sabre

Well, I've only run about 3 events with these rotors, so 6 days with 4 - 5, 1/2 hour sessions each day....so I can't give you a really good idea on longevity, other than to say that mine are just fine after what I've put them through so far. Wish I had better info for you.

CO_VaporGT_09

Keep an eye on them! I really think they are PowerStop slotted rotors, maybe the cryo treated ones, as they say on the website the slots should go to the edge of the disc if they're still good, and as you can see above, my slots don't quite make it, so time to replace.

houtex

My only concern, re: replacing the rotors, is that if you're racin' them... that hot spotting changes the way that metal works. I wanna say it makes the metal more brittle? Not sure, but it isn't good.

Kinda would suck if one were to unfortunately explode... especially a front one in a turn... ouch.

It's your call, but I think I'd be dealin' with new ones, race rated, and maybe drilled and slotted too?

/edit: Oh, right, rear ones... Not front. Still. Dunno what that heating/cooling will do to change it.

CO_VaporGT_09

Some accurate, some not...

Very right about the brittleness, and there's stories of the old Fox Mustangs being used as stock racers, OEM sized brakes, where the rotors WOULD explode, sometimes on track, sometimes while cooling off in the paddock, so definitely a valid concern -- I'm switching out to some blank, OEM quality ones, $36 a pop, so cheap and easy to replace (this is generally accepted as the best option for stock brakes in particular).

There aren't really any 'race rated' rotors for the rear brakes, I thought Roush were good and probably were, maybe I just used them too long.

Drilling rotors is actually horrible for the track, though makers like Porsche, Corvette, etc frequently equip their street cars with them. They actually REDUCE the mass available, which is good for unsprung weight, but not for what the disc does -- absorb and dissipate heat. They also tend to crack from one drill hole to another.