I've had a squeek from my uprated (24mm) rear arb since I had it fitted. I'm pretty sure that it is something to do with the 'clamps' - does anyone else have this problem and have you managed to solve it? Its very irritating, and I am loathed to replace the original arb as I know that one of the bolts going into the rear radius arm is knackered...
The brake proportioning valve is used to balance front and rear brake loads during periods of hard braking. When the weight of the vehicle shifts towards the front of the vehicle during the quick deceleration of hard braking, the rear wheels have a tendency to lose traction. The proportioning valve is able to reduce pressure to the rear brakes to prevent rear wheel lock up when the brakes are heavily applied. H that helps.. woody