Rich at High Performance House sold me Porterfield pads for the front of my car (a noticeable improvement), but he did not think they are necessary for the rear brakes.
It seems to me that I could also benefit from putting them on the rear giving me overall improved braking instead of just improving the fronts.
Is there some reason that the pads are not recommended for the rear brakes?

Depends on your brake bias.

I'm running them in the rear also, plus my bias is different from stock (more bite in the rear).

It's a bit of trial and error. The last thing you want is the rears lock up on you first when braking hard.

Every car is a bit different, i had to try out a few different compounds to get there and you certainly can use different pads front/rear.
Andy

I'm running the R4 pads on the front and stock in the rear on my 74 (which has the stock proportioning valve) and I have no complaints. I'd give it a try and if you find that it's sub-par, then add the rear pads later.

Cheers,

I use both front and rear R4S pads on the 914 and 911.

I like to use the same pad compound front and rear. I believe that the original engineers intended this.

Eric sold me a set from the front and rears for my 76. I am sure he would not of done that if he did not believe that was the best thing for the stock brakes for better stopping as I told him the brakes sucked compared to my 86 Carrera.

Bob