Went out to hammer the Porterfield RS4s today for the first time to bed them in and finish off the dark dust which I believe is the silver cad plating from the new rotors I put on at the same time as the pads. I learned some things:
1) As expected, the Porterfield R4S is not as effective as the stock pad. The stock pads are DANG GOOD! Just SO messy.
2) Even though not as effective over all, the Porterfield R4S does have a kind of benefit for non-ABS cars arising from that lack of bite - they are easier to modulate on the edge of locking up, so you should be able to threshhold brake more accurately. At the pedal pressure I was applying today I would have expected the stock pads to lock up, but the Porterfield R4S was not even close.
3) Even with Tom's 40mm rear caliper upgrade, the inboard area of where the rear pad contacts the rotor has still not completely scrubbed off the cad plating - even after 15 or so miles of regular slow driving and three hard brakes from 80-100 mph down to about 30 mph.
4) I did not do any slower speed-to-lock up testing today, but from the feel I got I think I might have stumbled on to the last piece of the non-ABS braking puzzle - the passenger front locking up first. At the same time as the brakes I installed Aldan adjustable coilovers on the car. One of the many reasons I did this was because the car sat lower on the driver's rear. I have the spring perch on the rear driver's 7/8" higher than the passenger side and now have the driver's side wheel arch about 1/4" higher than the passenger side while the driver's side frame rail is still just slightly lower than the passenger side. OK long story but what I think I have done is rock the car on the driver's front-to-passenger rear axis effectively putting more weight on the passenger front which gives it a bit more bite and I am guessing that when I do some lock up testing I will get both front at the same time (could STILL use more to the rear I think even with Tom's 40mm caliper mod).