Been following this for some time, and I'm confused by some of the comments made that just done jive.
First I'll tell you that a change in suspension and or a change in weight distibution WILL have a significant effect on how a car brakes. Most FWD cars see extensive front braking simply due to their balance. Add some larger rear brakes and as it was pointed out; you may be seeing your own tail lights.
The term "appplying the same clamp forces" or whatever it was has no real impact on what is happening here. Clamp loads are not what this debate is about. BIAS is what is changing. Meaining if you car is at its limit at 80/20 bias at the point of rear lock up and we throw 300lbs of sand in the trunk, then the numbers will likely change to 70/30. At this point the same amount of line pressure will be working the rear brakes harder, so we can then add more line pressure to get all of them to work harder without the potential for lock up. Intesting test; brake testing with and without weight in the trunk.
Now if we road race the car and gut it out pretty heavily, this does not really aid us as hoped as most of the weight removed is in the area we need it. But that's a trade off for overall reductions. So we put some Konis on the back and valve them stiff to help control body roll or pitch into a corner. This keeps the tire patch and weight in contact with the road longer thus allowing the rear brakes to contribute to the working being requested.
I've got some really neat formulas that can show what changes are netted to the brake torque when we upsize either end of the car, not a true change to the overall package as real world braking also has to take into account this weight issue and its biasing of the brakes.
Having been a SHO dude for years we often spoke of the 'prop valve' in the rear of the SHO, bunk. It's not a proportioning valve at all, it's a simple height sensor. When the rear of the car goes UP the valve shuts OFF the rear line pressure. This means nearly zero line pressure to the rear under extreme condtions. But if we bypass it, the car slows much better under moderate conditions, then ABS takes over under extreme loads. This shows us that the weight transfer to the front is so extreme that we cannot use what's back there. Unless we find a way to control that shift of weight under braking- stiff struts out back, heavy springs up front, reverse rake, whatever it takes. But each of these may have its own drawbacks elsewhere.
Lastly, larger brakes in the rear won't make your car a racer no matter how hard you try, they will 'enhance' the ability of YOUR car (depending upon other mods) to take advantage of what you may be able to achieve. I doubt a simple disc to drum of stock parts will have a significant effect one way or the other. However I'd run the same MC and any proportioning valve set up off the disc car when doing the change.
