The factory proportioning valve is installed in the front circuit to limit the front braking power as the rear calipers are woefully undersized. In most applications with correctly sized braking system the proportioning valve would be in the rear circuit.
If you are retaining the stock brakes leave it in the front circuit. For an aftermarket upgrade I like the HiSpec calipers from the UK as they incorporate a parking brake that is designed to meet the MoT rolling road resistance/hold test.
Is this a good option?
Everyone says on this forum that the kits offered by SACC Restoration are excellent. However, I am not sure of the usefulness of 6-piston calipers on the rear of a car which does not have ABS and where the risk of wheel locking is therefore significant, unless you are an excellent pilot. From my point of view there is a way to have a very good system for much less money with used equipment.
Yes my calipers fit inside the original rim, they are front calipers from Renault Mégane RS II or Clio RS III (Brembo like the Porsche); I bought them for €200 on Ebay. I made the brackets myself to fit them. They do not feature a handbrake and I installed a hydraulic handbrake. If you want to keep a completely independent handbrake you must install a mechanical caliper specifically for that or an electric caliper from Tesla; this is relatively easy given that the hubs have four attachment points each; There are several thread that cover this subject.
Speaking of HiSpec Calipers in the UK; on the web site they mention the issue of “too much caliper” for a given rotor diameter. It seems more is not necessarily better. Also, it should be noted, their rear calipers with integral parking brake, as well as their parking brake spot caliper, both use the OEM cable routing, in a Pantera application. I also understand they have the appropriate adapter brackets, for the Pantera.
