Larger Rear Brake Rotors?

Discussion in 'Brakes, Wheels and Tires' started by VoodooBoss, Dec 1, 2013.

  1. antman450

    antman450 TMO Race

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    FWIW I run G-Loc R18 front and R12 rear. I have no issue with ABS or bias. I do have the racing ABS module though. Front and rear pads wore exactly the same, so i think on the smaller rotor, the rear would have gotten hotter and worn faster. I use DBA 4000 1 piece rotors that are slotted.

    I did the GT500 brackets and DBA rotors that are 13.8 inch. I have not had one bit of noticeable extra rear bias under very heavy braking.
     
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  2. smallblock

    smallblock TMO Advanced

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    I have had stock, gt500 13.8”, and performance friction PWC 2pc rear brakes on my GT.

    Gt500 with street pads on all 4 corners activated ABS prematurely on occasion. On track with aggressive carbotech front pads they worked well will no noticeable abs triggering. This was with 14” Brembo front brakes. Keep in mind the 13-14 GT500 not only came with 15” front brakes, but also a taller rear tire O.D. increasing front bias. Anything but ceramic street pads produced occasional groaning in turns. Also, some binding in reverse. Driven hard with 305 pirelli slicks caused rotor to contact the caliper bracket.

    I picked Dean martin’s brain and he said that the GT500 13.8” is too much rear bias. He had also never seen the rotor contact the bracket. They never ran more than the 12.9” on the race Cars. I ended up buying a PWC Performance Friction kit from them (with wider rotor bridge) and installing S550 calipers on GT500 rotors in the front. Changed out axles just to be sure but they appeared to be in great shape. Balance is excellent. Rear rarely produces groan with aggressive GLOC pads. No noticeable binding in reverse.
     
    Last edited: Nov 7, 2018
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  3. Surfergeek

    Surfergeek TMO Race

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    I am going down the same path as smallblock on my rear brakes. Ordered the same PFC World Challenge rear brake set-up through Filip at Cortex Performance.

    I have been experiencing groaning in turns and binding in reverse using the Steeda 13" kit (installed before the GT500 rotors became a real option), excessive pad wear in the rear.

    I think this PFC kit is the best thing that can be done for the rears, to beef-up the factory caliper, get a 2 piece floating rotor back there, and more rotor surface area with the 12.9" disc. https://s3.amazonaws.com/ccommunications/Build+Sheets/20150408_LAT_Mustang+Build+Sheet+F&B.pdf

    It helps with the deflection under turning and gives more surface area for a cooler rotor.

    I discovered it by seeing it on Doug's car and asking him about it at a track day we did in December. He has had no complaints or issues on his high power and heavy GT500. Because I have the blower and my car for now is most definitely still a street car, it's carrying around a lot of extra weight. Talked to Filip about my issues and short of putting in the full floating cambered rear axle (Allows for proper fitment of proper racing brakes in the rear, but spendy and overkill for most of us), this is the best that can be done.

    His suggestion if I didn't want to do the full kit, was to go factory sized (not GT500) Girodisc 2 piece rotors and it could solve my issues, but best solution short of the cambered rear axle, was the PFC kit. They also include the kit as a basic option with the cambered rear axle, and you can step up to upgraded calipers from there.
     
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  4. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    What sort of binding in reverse was going on and how did you find it?

    Was there any groaning happening in reverse either with or without braking?


    Norm
     
  5. Surfergeek

    Surfergeek TMO Race

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    The groaning/binding in reverse was happening while driving the car in reverse with no brake applied. Once the brakes were lightly applied the binding would stop. It was very apparent, very loud, and could be felt in the car.


    Sent from my iPhone using Tapatalk
     
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  6. VoodooBoss

    VoodooBoss Rick Moderator

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    I had the same groaning issues in reverse with the larger rotors on my Boss. It bothered me so much I took them off. That PFC setup looks pretty sweet.
     
  7. Surfergeek

    Surfergeek TMO Race

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    What was interesting, is I didn't really develop the problem until I switched to some more aggressive pads in the rear / my driving got faster. At first I had no issues with the larger rotors in the rear.

    Doug has reported no issues with his PFC setup and is using aggressive pads in the rear (PFC Race Compound) so I should be good to go.
     
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  8. smallblock

    smallblock TMO Advanced

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    FWIW, I never had any noise with the GT500 rear brakes when I briefly used ceramic pads, not a peep.
     
  9. antman450

    antman450 TMO Race

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    Mine grind in reverse too but up to where the rotor finally notched the caliper enough to not grind. Didn't care since the I don't drive the car. Only time in reverse is getting off the trailer.
     
  10. bulldogracer

    bulldogracer TMO Intermediate

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    Can someone share the PFC kit P/N or where I can find it on the Cortex site. Thanks
     
  11. Surfergeek

    Surfergeek TMO Race

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    It’s not on their site. Call and ask and they can get you a quote / invoice over the phone.


    Sent from my iPhone using Tapatalk
     
  12. smallblock

    smallblock TMO Advanced

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    https://s3.amazonaws.com/ccommunications/Build+Sheets/20150408_LAT_Mustang+Build+Sheet+F&B.pdf

    Call Kohr Motorsports, they know all about this kit. Its a piece together set that you wont find on any website.

    I am extremely happy with my PFC kit. The car sees road and track duty, and even with Gloc pads on all the time they are dead silent no matter the temperature or weather. It must be noted that the harmonic dampers, and the caliper reinforcing brackets are installed. When I ran the GT500 kit and race pads they were extremely annoying on the street, and as mentioned above, rotors hit the caliper bracket on the track.
     
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  13. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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  14. Coz

    Coz TMO Race

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    The pre-2013 S197 rear brackets had to be ground down a bit to provide clearance for the larger diameter rotors. For 2013-14 the rear caliper brackets & calipers were the same for all submodels and there were no clearance issues.

    I've never had any noise issues in reverse.
     
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