Car is Toyota WSR. Stock MR2 calipers. Tilton 3/4" bore masters (front and rear w/ cable controlled bias). Almost new rotors, almost new Porterfield R4 (or whatever number is their standard race compound). Car has been sitting in a detached garage for maybe 4 or 5 years.
OK my best guess was calipers. Replaced one, rebuilt the others. Same results.
Next I look at rotor surface. It's pretty shiny and a bit heat checked... nothing that I haven't ever seen before on street cars and it never turned the brakes into junk. But I lightly abrasive blasted them and sanded the pads. Have not yet test drove (32deg out and parking is only empty on Saturdays).
QUESTION 1) Can rotors glaze up to the point that they need a ton of pedal force to brake?
Next I take a lab grade pressure transducer, make special adapters to tap the lines right at the calipers, dump brakes fluid all over freshly painted calipers and other parts while trying to hold too many things by myself. Unless this guage is whacked, I have about 400 psi line pressure with probably 200 lbf on the pedal. My calcs show 5.67:1 pedal ratio, 2x .44 sq. in. masters. Math says I should have 1288 psi to each of 2 systems with 200 lbf on pedal. I have about 400 psi on each system... very close to each other.
QUESTION 2) Is it possible that hydraulic efficiency is as low as 31% owing to piston seal friction?
I remove both masters and disassemble. Front master shows a wear "land" where the pistion normally stops while braking. Aha! Seals must be expanding and locking the piston there. But rear master looks perfect. I put a kit in rear, replace fron twith new. Just checked line pressure and it's 400 psi on front exactly where it was before. Haven't even had the urge to check the rear because I am certain it will be the same as well.
WSR guys do not know expected line pressures but the system is all factory Toyota but now with Tilton masters.
QUESTION 3) Is it possible the stock Toyota ran with 400 psi line pressure? Tilton and Wilwood both want to recommend (when designing a new system) 1000 psi.
Hope someone here can help me sense of all this. I will test drive the car tomorrow but I am not really optimistic other than it should stop well at first due to roughening the rotor surfaces.