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I think that depends on the valve it was originally equipped with. There are a couple of them that are or would be sketchy with F/R discs. DO NOT use the '87/'88 Shelby Z "white" tagged valves. They WILL cause premature rear lock, especially without staggered pad compounds.

The best one IMHO that I've found is the "yellow" tag valve used for '90 (and other years) disc/drum cars.
 

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Discussion Starter #3
Ill have to look what valve my 94 p body parts car has. The receiving car is an 88 Sundance.

The setup im putting on the car is non-vented rear disc with minivan calipers and brackets with 11" 5x100 rotors. Minivan master cylinder too.
 

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Discussion Starter #5
Im sure it will work. Id rather take care of the prop valve and brake lines while the powertrain and k frame are out of the car. That thing isnt an easy job on a fully assembled car as we all probably know.
 

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I swapped 89 GTC brakes disc front and rear on to an 88 disc/drum car without changing the valve and it stopped fine, even in panic mode.
I'm not saying it won't stop. I'm not even saying it *will* cause you issues. However, from personal experience on a race track, car being 55/45 F/R, using the same compound pads front and rear (Porterfield R4S) with the original '88 "white" tag proportioning valve along with tire pressures that were good for those activities that the rear brakes would lock before the fronts under threshold braking, especially after about 3 laps (once the brakes had heated up and the compound was at a more ideal operating temperature).

I had the same experience when I swapped to Carbotech XP8 pads in the front, but left the R4S pads in the rear and that was WITH the "yellow" tag proportion valve. I swapped to a super cheap organic compound in the rear and THAT solved the issue.

Now, a car that's heavier in the rear, has more downforce in the back, or simply just has better traction probably won't see this issue as much but I made it a point to bring up my weight distribution to make a point...my car ISN'T that light in the rear.

I do admit that the compound was certainly a factor here, and parts store pads will probably never exhibit this issue, but *I* know it exists.

I also have experience with a friend's old '88 Shelby Z that I spun out at around 80mph due to the rear brakes locking before the fronts on a cold road surface with possibly some light dust (dirt, not snow). I have also had other people say that they have experienced similar issues with the balance of the Shelby Z brakes.

Take it as you will. YMMV. I'm just letting people know some possible outcomes from real world experience and since we are talking about the biggest safety item on a car (IMHO)...I think it's fairly important! :thumb:
 
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