Welcome to T&B,
Odin.
Here's some information about your vehicle:-
http://en.wikipedia.org/wiki/Bedford_SB
http://wakefieldfiles.co.uk/bedford-sb.htm
http://wakefieldfiles.co.uk/bedford-sb-list.htm
http://www.travellerhomes.co.uk/?s=183
I'm afraid I don't have any details about your braking system - it's many years (45) since I was involved and I no longer have access to the information.