Warped front brake rotors

[ByeEnzo]

I spent this weekend in a HPDE course at Motorsports Ranch. After several previous track sessions (about 15 half hour runs), I recently changed out my front pads. My original stock pads were about 50% worn. Went to a set of Porterfield R4-S pads up front prior to this weekend. Also running Hoosier R6 slicks. Towards the end of this weekend's fun I noticed quite a bit of shudder on hard braking on the track. Sure enough my front rotors are warped. The vent holes had filled up with brake dust from the softer grippy pads and I think this over heated the rotors. I used these pads as a compromise between street and track. I am probably going to replace the front rotors with a new set of OEM rotors and go back to the Ford brake pads, accepting less braking performance in exchange for durability, since I plan on street driving the car. My thinking is that the original setup worked fine with my driving style, and pads in the long haul are cheaper than rotors. My rear rotors and stock pads are just fine although I suspect brake bias is quite a bit to the front on the stock setup. Anybody else have a problem like this with their GT? I could go to a different set of rotors (slotted 2 piece) and pads up front but don't want a bunch of squealing or loss of low temp performance. Any thoughts would be appreciated.

On a brighter note, the highlight of the weekend was me tailing a modded C6 Z-06 during one of the sessions. The guy was overdriving the car so bad, trying to get away from me, that he finally went spinning off into the weeds. My instuctor got a kick out of that.

 

[ByeEnzo]

One other question

Is turning the warped rotors an option? I think they would be thinned making overheating a problem again with track use.

 

[shelbyelite]

I can probablY R&R them for you if you like. I had a set of warped rotors on a Ford GT one time and turned them and they have had many happy miles since. Got to be careful turning them as they are drilled rotors, but it can be done if you know what you are doing. If you are interested, let me know. I will be happy to help.

 

[barondw]

Next time you get rotors for driving events have them cryogentically treated. It helps with wear and overheating. Well worth the investment if you do multiple track days. Rotors only not the pads. No negatives for street driving.

Depending on how badly they are warped they could be turned, but I would then keep them as a back-up set. Also go with slotted not cross drilled because of cracking near the holes, a very common problem, under heat.

Stock pads are okay to use, but have a spare set as you can go through them in less than a day.

 

[snaproll]

you might find that getting them really hot might get things back to normal. Rotors don't usually warp from track use but sometimes get an uneven transfer film layer or whatever. You get the shakes. But it can go away. Last time I was at Road America (not in GT) I swapped pads and had some pretty bad pulsing. I just checked to make sure I didn't have a loose nut (other than behind the wheel) and kept on them to "burn" them in.

 

[ByeEnzo]

I may try snaproll's idea of really jumping on them next time out. I did at least 15 track sessions on the stock pads with no problems whatsoever. The minute I put the Porterfield's on I had a very grippy, pulsing feeling even under light braking. I even thought my ABS was going off the first time I drove on the street. Did 8 sessions this weekend with the problem worsening as time went on. Was advised by Livermore Performance that I might have uneven transfer of pad material to the rotor. There are definitely uneven patches on the disks. I could go with slotted rotors on the front, running stock pads again. The Porterfield pads have a smaller contact area than stock with slanted leading and trailing edges. This may have led to too much heat in too little a contact patch.

 

[cobrar1339]

Material transfer is not uncommon. We see it one street cars where one swaps one material for the next. It will almost feel as if it bites, skates, bites.
A very light turning of the rotors will remove the old material. In a jamb on a street car a some heavy steel wool and brake cleaner often works to loosen it up. If it is just a transfer of materials it will eventually burn off. You are braking hard enough when you feel the ABS come on.


One other note has to do with bedding the pads in. If you follow the bed in instructions, they want you to let them cool overnite. So, if you just slap on a set of race pads on track day you will not get everything they have to offer and often some headaches. Cooling between sessions is not enough for most pads. I see this alot at open track events. Bed in instructions are on most mfg sites, Hawk, Carbotech, Porterfield. Some times they forget to put them in the box.


The Cryo rotors I like and run them on a couple cars. I have had them on fleet vehicles with good success as well. I was introduced to these by a BMW team around 94. They used these to solve the know warping problems on the 96-98 M3. Some will say they do not work. But for me they do.

On the C5 ZO6 with very aggresive pads ( PF01) I would chew up a set of stock rotors and crack the rears in two weekends at BW. With the cryo rotors I went 6 events before finally cracking a rear. Replaced with the same and still going strong after 5 events. I am using the Powers slot rotors cryoed. The cost is not real high IMO. To find out more go to Frozenrotors.com the owner is a track guy and runs as Z06 or at least he did, he has done some laps in a GT as well. If you decide to go this way it's pretty easy, he orders them from Ford, Gm or whatever you want. Treats them and ships them to you. He seams to get a good deal on the rotors themseleves. As I recall, he is in the Minnesota area. Maybe this time of year he just leaves them on the porch. :lol

Regarding pad material. The PF01 is a great pad but will take it's toll on rotors quickly. I have run Porterfield's pads many times and they are like bricks when cold, but great when hot. The two above I do not recommend for tracks days for those reasons. I know Kyle from Stillen ( Forum Vendor)had some recommendations, I would check with himfirst as they have real world experience. On the Z06 the most rotor friendly pad with the best feel has been the Carbotech. I have not tried to source these for the GT yet. But would be tempted to try them or something Kyle could share experience with. Talk to the tech dept a good tech will want to know weight of the car, tire selection, caliper, weight distribution, etc when suggesting a pad compound. Unless of course they already have experience with the car.

Good luck, keep us posted.


Track Newbie tip:
One more tip for those that have not done many track days. Use the whole cool down lap and stay off he brakes as much as possible. Do not use the parking brake after coming in. Let them cool before you do.

 

[ByeEnzo]

Cobra,

Thanks for all the tips. I may try turning them down or the steel wool trick. Somebody suggested getting water on them so a layer of rust is seen and then getting on them hard to scrub the rotors. If that fails I'll get new rotors and may go back to stock pads accepting the wear and braking characteristics. Thats the compromise with a street driven car that is also tracked. Once my Caterham R-500 Ultralite is fully sorted, I will be taking the GT to the track less anyway. It is such a blast on the track though and people commend me on actually driving it in DE's rather than having a garage queen. BTW, I definitely follow your advice about cooldown laps and staying off the e-brake. Thanks,

AC

 

[ThatPhilBrettGuy]

Always a good read to be had here http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

 

[barondw]

Always a good read to be had here http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

Good post. As mentioned in article make sure back side of rotor and hub are flat. Always clean, minimally with a wire brush to remove any residue. Also perform with new rotors, new doesn't mean that there isn't crud on the back side.

 

[cobrar1339]

Excellent link :thumbsup

 

[ByeEnzo]

Thanks for the link...very informative. I took off my front wheels today and thouroughly cleaned the rotors with steel wool and brake cleaner. Still burnished appearing areas on the rotors. Then I went and tried to bed in the brakes again, but still a lot of shudder up front. I think the change in compounds resulted in an uneven transfer of pad material as the Stoptech article suggests. The rotors will need to be minimally turned to get rid of the high spots. I'll keep them as backups. I've got Maurice at Duval Ford in Fla. sending me new rotors at $155 each. A set of stock pads costs $210. Should be able to do the swap and be up and running smoothly.

 

[PL510*Jeff]

Is turning the warped rotors an option? I think they would be thinned making overheating a problem again with track use.

The rotors can not be turned down according to the service manual. They should be replaced with the third brake pad change.

I've had to clean out the crossed drill holes. A bit time consuming. But that's the price you pay on when you go to the track. Way too much fun.

 

[SFLGT]

That's true. According to Ford they can not be cut. Must be replaced for any vibration problem. Remember though rotors are a warranty item. Pads are only 12/12

 

[snaproll]

The rotors can not be turned down according to the service manual. They should be replaced with the third brake pad change.

I've had to clean out the crossed drill holes. A bit time consuming. But that's the price you pay on when you go to the track. Way too much fun.

I wouldn't worry about cleaning the holes. They aren't good for anything anyway. Just trying to save you some time . . .

 

[ByeEnzo]

That's true. According to Ford they can not be cut. Must be replaced for any vibration problem. Remember though rotors are a warranty item. Pads are only 12/12

I may take the bill for the rotors to my local Ford dealership and ask for reimbursement. The local guys charge way more than Maurice does, but if its under warranty, it's worth a try. The 2 bolts that hold on the calipers are also one time use items according to the shop manual. Has anyone changed out their own rotors? Doesn't look like too hard a job. Need some torx sockets to get the rotor and caliper off. Does it actually say somewhere not to turn the rotors? They are 32mm thick and the shop manual says that min. thickness should be 30mm. Not that I think I need 2mm of metal shaved off. Personally I have a low threshold for tossing the old ones, as any thinning is liable to heat sink them even more.

 

[SFLGT]

Yes it does. The Ford shop manual say do not resurface the rotors. They are replacement only. you are also correct that the caliper bolts are one time use. I replace them every time I take a caliper off. They come in package of 2 bolts if you order them.