Cobra R rotors warped

spederman · Jun 3, 2007

I have the Cobra R front brakes, basically its the Brembo Gran Tourismo kit with 13 inch slotted rotors with 4 piston Brembo calipers. I have had them on for about a year. I rarely get on them very hard. I went to a road racing track the other week and that was the first time i used them like they are supposed to be used. The car still drove fine for the 1 or 2 weeks after. Now only upon braking, the steering wheel shakes. It started doing it at first only slowing down from high speeds 70+. But now it seems like even 50mph it shakes. I know that is usually a sign that the rotors are warped. But these are freaking expensive brakes that are made to be driven hard. Why would they warp? Plus since they are slotted, i cant really re surface them, so what do you do? Just toss hudreds of dollars worth of rotors in the trash and get new ones?

Back2Mustangs · Jun 3, 2007

I don't think the rotors that come with that kit are vastly different than a standard replacement rotor you'd buy for any Cobra. I could be wrong, but the only way to know for sure is to have whoever engineered/produced them (Brembo) explain the materials used and the process in which the rotors are created. No rotor should have warped so quickly so maybe one of them is defective or cracked. Maybe you should go have your front wheels balanced with an alignment before replacing the rotors. Possibly you threw a wheel weight at the track or broke a belt in a tire... ? I'm just fishing for other reasons for the vibration. If it really is a warped rotor, use this as an opportunity to buy some nice two-piece, light-weight rotors.

Ordie · Jun 3, 2007

Does the brake pedal pulse when you get on the brakes?

Thundermouse · Jun 3, 2007

spederman said:
I have the Cobra R front brakes, basically its the Brembo Gran Tourismo kit with 13 inch slotted rotors with 4 piston Brembo calipers. I have had them on for about a year. I rarely get on them very hard. I went to a road racing track the other week and that was the first time i used them like they are supposed to be used. The car still drove fine for the 1 or 2 weeks after. Now only upon braking, the steering wheel shakes. It started doing it at first only slowing down from high speeds 70+. But now it seems like even 50mph it shakes. I know that is usually a sign that the rotors are warped. ? But these are freaking expensive brakes that are made to be driven hard. Why would they warp?

First, all brake rotors will warp, crack, become unusable etc. at some point when they put into extreme temperature ranges. Driving at the limit on a road course will do this. Driving the streets won't. You're just gonna have to used to the fact that when you drive your car hard, rotors are a wear item just as much as pads are.

That being said, there are some things you can do to extend rotor life.
1. Do a warm up lap to get the brakes up to temperature slowly and evenly.
2. When you are finished, do a slow, slow, cool down lap. This will help cool your brake system.
3. After you are done with the track session and your car is parked, use a block of wood to keep your car still, not your parking brake. It will trap heat unevenly in your brake system -> great for warping.
4. Get some air ducted to your front brakes. This will make worlds of difference for life of parts and brake fade.

spederman said:
Plus since they are slotted, i cant really re surface them, so what do you do? Just toss hudreds of dollars worth of rotors in the trash and get new ones?

Yes, throw them away. Slotted, Drilled, dimpled, whatever; they are all worthless when it comes to durability on the track. Stick to a full surface rotor. If you buy more slotted rotors, don't expect different results. Did you ever stop to wonder why even brembo has a disclaimer on their website that warns not to use their slotted/drilled rotors on the track?

supastang03 · Jun 3, 2007

since they're slotted/drilled/dimpled...w/e, their integrity is much less than a full surface rotor. the smaller amount of mass makes it alot more succeptable to warp during influxes in temperature. stick to full surface next time...

Back2Mustangs · Jun 3, 2007

Do rotors commonly warp after one day of twisty-track use though? Maybe the ultra-cheap ones that you buy from AutoZone, haha. I'm hell on my brakes and I don't have troubles with warped rotors. Even on the streets I go through a set of tires in 12 months, brake pads about every 8 months. I ride my the stock brakes so hard some days that I have fade to the point of having no brakes at all and thats after just a 15 mile drive to work (which is all highway). I have yet to experience a rotor warp on this car. In past cars, I've had it happen quickly with the stock brakes... but from what spederman described, if his rotors warped that badly from one day of auto-X, I would think something wasn't right. I can't say for sure because I don't have enough road race experience, but it does seem pretty crappy that a year-old set of brake rotors is done in after one day of abuse.

markwsoil · Jun 3, 2007

I have the Cobra brake upgrade on my '98 GT, brand new parts with PBR two piston calipers and 13" rotors. I know it's not the exact same set up, but rotors of that size, especially driven exclusively on the street, shouldn't warp, and I'm having a problem with minor warpage with not 5,000 miles on them. It's weird how it can happen.

My daughter's '89 Fox body four cylinder is starting to show signs of rotor warpage as well. I can't imagine how you can over heat those rotors, but they're sure as hell warped. I hate front disc brakes sometimes.

spederman · Jun 3, 2007

OK, so full face rotors are a lot better for performance? But why do sports cars come with drilled or slotted brakes over full face? One guy at work has a C6 Z06 and it has drilled rotors all the way around, and so does my buddies Porsche Cayman S.

What are come great rotors that i can get in 13 inch that can handle abuse and still hold up? I see most places have powerslot or brembo. Are two piece rotors much better to get, and who makes those?

bdcardinal · Jun 3, 2007

the cars that come with "drilled" rotors have those holes cast into the rotor at the factory, they are not drilled after the rotor was cast like most of the cheaper ones. also a lot of tracks and racing orginasations are banning drilled rotors in general, unless you can prove they were cast with teh holes in them. i have seen some rotors where the holes are chamfered to allow for better cooling.

you can get 2 piece rotors from brembo, and some other places. 2 piece rotors are very espensive though. Join svtperformance and check out the open track section. also look into brake cooling mods. i have cooling ducts for my front brakes that i picked up pretty cheap from a guy on SVTP that makes them.

o and for people that want to know why tracks are banning drilled rotors, this accident was directly caused by a cheap drilled rotor cracking.

View attachment 382933

rconaway · Jun 3, 2007

I have the same brakes but haven't run them yet. However, I will tell you that without adequate cooling, they will warp faster than a solid roter. The rotors supplied with the brakes are are street roters. I don't know what type of pads are on there but I suspect they are street pads also. Keep in mind the car was street-legal first. However, the key here is that when you replace them, look for powerslot rotors and a harder pad. That should solve your problem and you now have a 4-pad caliper with 13" rotors.

hotmustang331 · Jun 4, 2007

Back2Mustangs said:
Do rotors commonly warp after one day of twisty-track use though? Maybe the ultra-cheap ones that you buy from AutoZone, haha. I'm hell on my brakes and I don't have troubles with warped rotors. Even on the streets I go through a set of tires in 12 months, brake pads about every 8 months. I ride my the stock brakes so hard some days that I have fade to the point of having no brakes at all and thats after just a 15 mile drive to work (which is all highway). I have yet to experience a rotor warp on this car. In past cars, I've had it happen quickly with the stock brakes... but from what spederman described, if his rotors warped that badly from one day of auto-X, I would think something wasn't right. I can't say for sure because I don't have enough road race experience, but it does seem pretty crappy that a year-old set of brake rotors is done in after one day of abuse.

WOW
WHY do you use your breaks that hard????? Do you just get going 70MPH and then down shift to 3rd and go WOT while at the same time applying breaks to stay @ 70MPH....and do that all the way to work . And man I bet you have to clean your wheels daily haha.

Im still on the stock pads....58000+ miles. My last rear tires lasted almost 40K BTW.

BennyBlown2v · Jun 4, 2007

hotmustang331 said:
Im still on the stock pads....58000+ miles. My last rear tires lasted almost 40K BTW.

Yeah, but you just just drive to work....then let the car sit for six months while you throw some whirley things on it

But yeah, go get some plain rotors - cheaper and work well.

Back2Mustangs · Jun 4, 2007

hotmustang331 said:
WOW
WHY do you use your breaks that hard????? And man I bet you have to clean your wheels daily haha.

I work in the center of the fifth largest city in Texas so from the moment I exit the highway to the the time I park in the garage, I'm on the brakes pretty hard. The loops and chicanes between the highway and the street signals are the most exhilarating part of my daily commute. Leaving downtown at the end of my day is just as invigorating.

rconaway said:
The rotors supplied with the brakes are are street roters. I don't know what type of pads are on there but I suspect they are street pads also. Keep in mind the car was street-legal first.

That is exactly what I suspected.

Kilgore Trout · Jun 4, 2007

Have them turned

Most likely you have glazing in spots and not warping.

Have you used a dial guage to measure them?

whyask · Jun 4, 2007

Funny you bring this topic up I have the same rotors and setup and have had to replace them already after year..But not after heavy track use...I used them on the track alot the last 6 months.. and they finally gave way... the rotors are not cheap either... what pads are you using since we cant use you're average freaking pad... I replaced mine with the NON cross drilled and slotted last month and Ive been to the track 6 times already...Nothing yet just the pads getting crappy again...they squeak SOOO BAD !!

Thundermouse · Jun 4, 2007

bdcardinal said:
the cars that come with "drilled" rotors have those holes cast into the rotor at the factory, they are not drilled after the rotor was cast like most of the cheaper ones.

Fiction. They are drilled after casting.

spederman · Jun 4, 2007

I have to pull off the rotors this weekend and i'll have them measured to see if they are warped. I was checking into new ones just to get a price range and they are $300 for the ones i have now. Powerslot also makes the same type that are cryo treated for the same price. 2 piece rotors are relatively expensive, for the baer eradispeed they are $500 a pair.

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