rear rotor warping

[Eugene]

I have an S197 track dedicated mustang with coyote engine and have been having problems with rear rotor warping. It has happened with 2 sets of OEM 13.8 inch rear rotors from the 2013 GT500 and another brand as well. It occurs on tracks that are hard on brakes of course, such as CMP in SC.

Anyone use rear brake cooling ducts? I know the front braking bias is substantial in these cars but clearly my rear rotors are getting lots of heat. Also looking for recommendations for rear rotors that won't warp easily. Girodisc? I use them for my front rotors. I don't want too much bite from the rear brakes if possible.

Thanks.

 

[67GTA]

I have an S197 track dedicated mustang with coyote engine and have been having problems with rear rotor warping. It has happened with 2 sets of OEM 13.8 inch rear rotors from the 2013 GT500 and another brand as well. It occurs on tracks that are hard on brakes of course, such as CMP in SC.

Anyone use rear brake cooling ducts? I know the front braking bias is substantial in these cars but clearly my rear rotors are getting lots of heat. Also looking for recommendations for rear rotors that won't warp easily. Girodisc? I use them for my front rotors. I don't want too much bite from the rear brakes if possible.

Thanks.

A bit more info needed - which mode are you running AdvanceTrac in? And what brake pads - front and rear?

 

[Eugene]

Front pads PFC and rear Hawk DPS. I used PFC in the rear but too much bite. No traction control.

 

[EF1]

Have you removed the dust shields?

 

[Eugene]

Have you removed the dust shields?

Yes, no dust shields in rear. I have the GT500 -3.8 rotors in rear. Hawk HPS pads.

 

[EF1]

I have pretty much same brake set up on my 2011 GT except for pads. I have yet to warp a rear rotor on at least a dozen weekends at CMP. Are you sure the rotors are actually warping? The reason I ask is I have had brake pulsing that I thought was warped rotors and it turned out to be an epas issue or uneven brake pad deposits on the rotors. Hawk HPS are really not up to track use on these cars. I did not realize how bad they were until I tried something else. Girodisk recently offered a 2 piece rear rotor for the 13,8” shelby swap. Contact Tim at OP Mustang for a set.

 

[67GTA]

I have pretty much same brake set up on my 2011 GT except for pads. I have yet to warp a rear rotor on at least a dozen weekends at CMP. Are you sure the rotors are actually warping? The reason I ask is I have had brake pulsing that I thought was warped rotors and it turned out to be an epas issue or uneven brake pad deposits on the rotors. Hawk HPS are really not up to track use on these cars. I did not realize how bad they were until I tried something else. Girodisk recently offered a 2 piece rear rotor for the 13,8” shelby swap. Contact Tim at OP Mustang for a set.

Spot on and exactly my thoughts. Rotors don’t warp. Brake pulsations are felt though uneven pad deposits on the rotor surface or lateral run-out in bearings. The stick-axle rear ends have plenty lateral run-out, just by design, and that’s why the calipers have to be floating style mounts.

Also agree the HPS are not up for track duty, and likely the reason for excessive pad transfer. I would scuff your current rotors clean with roloc cleaning discs and try a different rear pad.

 

[Eugene]

Thanks. I went to Hawk because I felt PFC in rear was too much. What recommendations for rear pads?

I am measuring the discs with a dial indicator and getting up to 24/1000 inch. Can pad deposits cause that much? I don't see a ton of pad deposit on them but I can scuff them. The signs are a little brake pulsation but much more of a steering wheel shudder. Front discs are girodisc and are good, 2-3/1000 inch "warpage." PFC pads on the front. So not just a brake feel but shudder of the steering wheel. Still just pad deposits and they can simulate 24/1000 or disc warpage?

 

[EF1]

What year is the car?

 

[EF1]

Steering wheel shudder is not warped rear rotors.

 

[Eugene]

2008. It is milder than front rotor, warping, causing steering wheel shudder. But I did change to new rear rotors in the past and it resolved the shudder.

 

[EF1]

Okay so you shouldn’t be plagued by the steering shudder issues caused by the 2011 early 2012 epas. I still think it is an issue with brake pads not actually warped rotors. Do you take brake temps when coming off track?

 

[Eugene]

Thanks, very helpful. Front girodisc rotors were 350-400* last week at CMP. Rear rotors were 300-350 I believe. Definitely not horrific. So scuff and Doric the rear rotors and change rear pads? Which rear pads do you recommend?

 

[EF1]

With brake temps like that I am assuming you are doing a full cool down lap before taking them, so you really do not know how hot they are getting. Next time come in a couple of laps early without a cool down. Have some one waiting just outside the fence with a pyrometer and check them hot so you know what kind of temperatures you are dealing with. I am currently running GLoc pads. R16 front and R12 rears. I have previously run pads from EBC and Hawk.

 

[Dave_W]

You can also use temperature-indicating paint in a stripe on the outside edge of the rotors.

Genesis Technologies Brake Rotor Temperature Indicating Paint

Specializing in performance upgrades for the 2015+ S550 Ford Mustang.

www.opmustang.com