Brakes, brakes but sometimes something breaks

garrittpwl

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Okay so here's where Im at so far. Long story short, bought a shit ton of parts in a bundle. managed to get 4 TBM f5 calipers in the batch (the giant ones).

Now I've got the fronts all setup using a 14 inch 2012/13 GT500 front rotors but the back is proving more difficult. I had planned on using 4 piston wilwoods in the back on a 12.5 inch rotor but the wilwood setup I have isn't complete and rotors are proving difficult to source.

I know I can make the front rotor work on the back using the extra two TBM F5's I have but then I will effectively have all 4 corners using a 14 inch rotor and giant caliper.

My thought is that if my factory NON ABS proportioning valve outputs 75% to the front and 25% to the rear that I can manage to make this setup work. Otherwise I will need to buy a proportioning valve to run the massive rotors and calipers on all 4 corners. This route believe it or not is appearing to be easier than making the smaller wilwoods work.


Any thoughts on this? (should be noted that I have a 100lb box of misc brackets that were custom made for this purpose so caliper mounting is not an issue)

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Mustang5L5

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My thought is that if my factory NON ABS proportioning valve outputs 75% to the front and 25% to the rear that I can manage to make this setup work. Otherwise I will need to buy a proportioning valve to run the massive rotors and calipers on all 4 corners. This route believe it or not is appearing to be easier than making the smaller wilwoods work.

Ford doesn't have the specs listed for it's combo valve in terms of what the bias is, but in general that was ultimately controlled by the differing brake sizes vs output through the valve. Typically those adjust your knee point. You're initial pressures will be the same front and rear, and as you increase pedal pressure the valve would restrict flow to the rear.

This is the knee-point graph of an adjustable WIlwood unit. I run this on my car. I would suggest this over the ford valve as you can guy those valves pretty easily using the valve that is typically marketed for Fox cars.

1707152132397.png

If you'll notice the adjustment really just changes the point where the rear brakes will see less pressure than the fronts. But in every example, the initial pressure starts the same. The ford valve is similar, but you don't know where along this graph it would fall. Equal pressure isn't necessarily bad, but manufacturers would compensate for it by putting a smaller rotor or caliper. If oyu have 14" rotors all around and the same calipers front and rear, that's a awful lot of rear braking power, especially on a car without ABS
 
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garrittpwl

garrittpwl

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If oyu have 14" rotors all around and the same calipers front and rear, that's a awful lot of rear braking power, especially on a car without ABS
This was my thought as well. Got a link to the one you're running? As for the ford one, I'm not overly worried that I wont have a graph. I feel like I could remove a bleeder and hook a gauge up to the port to find what the pressure actually is. The ease of the Ford one would be that it is a single input/output and I won't have to redo my front lines.
 

Mustang5L5

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I run this one. (WIlwood style Knob)


There's a few with different fitting sizes. I don't know what you'll need for your brake lines. I installed mine on a union that ran to the single line running to the rear. At some point (1996 or 1997) Ford converted non-ABS cars to also running two line to the rear so hopefully if your car is non-ABS you only have 1 line.
 
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garrittpwl

garrittpwl

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I run this one. (WIlwood style Knob)


There's a few with different fitting sizes. I don't know what you'll need for your brake lines. I installed mine on a union that ran to the single line running to the rear. At some point (1996 or 1997) Ford converted non-ABS cars to also running two line to the rear so hopefully if your car is non-ABS you only have 1 line.
I have an 96 with factory NonABS. It has a single line to the rear thankfully.
 
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