Brake residual pressure valves

Hi all,

I want to fit 4 wheel discs and am concerned about residual pressure holding the calipers on at the rear.

I know drum brake systems usually have a residual pressure valve in one form or another. Is this in the lines or in the master cylinder in a type 1? Or is there no residual system? A brake guy told me there should be something, but then he's not a VW expert, just a brake expert!

It's a '68 with a dual circuit master cylinder.

Thanks, Marc.

If it is a 68 disc brake master cylinder it does not have a residual valve, as far as i know they were only fitted to and latter beetles with drums all round, i run a standard disc brake master cylinder on my car with four wheel disc's.