Gosh who dug up this old thread its more than a year old ? However still valid. Since posting the thread last year I have done a lot of research into the rear brake set up. I stuck with the Girling Claw Calipers until the last Llandow day March 2003 and that was the final straw for me. I had taken advise from a very well known race team and a brake specialist who both advised me to go Pagid RS14 pads all round, uprated master cylinder, brake proportioning valve in the rear circuit, flexible rear brake lines and finally strip and clean the entire system and refill with Castrol SRF. In addition I noted that my discs were fouling the inside of my calipers when hot so these were reduced to gain clearance. The result excellent fade free braking effort with good feel from both cold and hot on and off the track but sadly after a few reasonably quick laps the spongy peddle returned and the brakes needed bleeding yet again.
I have formed the view that I am wasting my time with these calipers as they were never intented for this type of extreme use and as a result will never be up to the job. The piston has a large flat face that is in direct contact with the back of the hot pad, its made of chrome plated cast steel and readily transmits too much heat ito the caliper. Behind the piston inside the caliper is the handbrake mechanism this traps a small amount of fluid between the hot inside face of the piston and the locating plate for the handbrake mechanism. This fluid gets very hot and cannot convect this heat easily throughout the rest of the fluid in the caliper body resulting in localised boiling and the gas produced gives the spongy peddle and is very difficult to bleed it out without inverting the caliper.
IMO fitting the Pagid pads into the Girling Claw Calipers was bad advise and has in fact made things worse, sure they give excellent bite but the extra heat that they create causes problems.
I am currently fitting uprated rear brakes and will report on my brakes after Cadwell on the 6th May.
Rob
SvenDriver giving me advise whatever next, you cheeky Monkey!