11.65" rear disc upgrade - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 5 Old 08-26-2019, 02:54 PM Thread Starter
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11.65" rear disc upgrade

i am looking to convert my rear to cobra style 11.65" disc brakes but keeping the stock brakes upfront on my 93, would there be any braking issues running larger diameter brakes in the rear than the front? I would use the 1" 93 cobra master along with proportioning valve.

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post #2 of 5 Old 08-26-2019, 05:02 PM
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I would gut the stock proportioning valve and get the adjustable willwood valve. you can customize the bias you need for your car.


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post #3 of 5 Old 08-28-2019, 04:25 PM
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The short answer is yes. Brake torque bias will be 64.7/35.3 F/R. Typically, we want a Mustang to have about a 70/30 brake torque bias. The imbalance means that there is more rear bias for a front heavy car than there should be. The result will be poor stopping distances since the front brakes are not contributing as much as they should while the rear brakes are likely to lock in dive (rear jacking). Keep in mind that the prop valve cannot correct brake torque bias imbalances. The prop valve can only move the knee-point (point where pressure is reduced in panic type stops) up and down the rear brake pressure slope. If not in a panic stop, the prop valve is non-active pass-through.

With the above said, this can be done but the risk of a brake induced spin-out goes way up. You should remedy the imbalance with a Cobra front conversion as soon as possible.
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post #4 of 5 Old 08-29-2019, 03:13 PM
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Or running less aggressive pads in the rear than in the front would be a cheaper/easier way to address the front/rear bias.

And yes, I realize that's kind of counter-productive, but it's an option.

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post #5 of 5 Old 09-06-2019, 04:33 PM
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For what it’s worth my 88 notch is running an 01 cobra irs outback with stock 93 calipers in the front and I do track days with no issues running back to back sessions. The front pads are hawk hp+ and the rears are parts store pads. That being said I do have sn95 spindles in the garage just trying to figure out what brakes I want to do on the front.
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