Brake Proportioning Valve, Good bad or ugly Options

[Charles Freeborn]

So, on to the brakes in this new car. It still has the OEM proportioning valve for the rears. As I understand when the brake pressure reaches a certain limit (500 plus psi as I recall) it stops sending fluid to the rear calipers. My first question is does it stop and hold at that psi leaving the rears engaged to that level while allowing fronts to get more input, or does it drop the rears to 0?
The other consideration is to use a manual valve such as the Tilton. If going that route how does one determine settings without chancing spins or other drama?
Thanks.

[infraredcalvin]

So, on to the brakes in this new car. It still has the OEM proportioning valve for the rears. As I understand when the brake pressure reaches a certain limit (500 plus psi as I recall) it stops sending fluid to the rear calipers. My first question is does it stop and hold at that psi leaving the rears engaged to that level while allowing fronts to get more input, or does it drop the rears to 0?
The other consideration is to use a manual valve such as the Tilton. If going that route how does one determine settings without chancing spins or other drama?
Thanks.

Not positive on the OEM system, but I think the pressure holds in the rear, while transitioning more to the fronts.

Both my track cars use the Tilton (or close version of). I have not messed with either setting from what the PO had previously set (its near neutral on both) but seem to have a nice front to rear balance.

The FAT -4 has Wide A vented fronts, M vented rears with a 19 mm MC, the -6 has 993 TT fronts and rears with a 21 mm MC, so calipers are well balanced from get go.