A twin power valve assembly for a hydraulic braking system having a single body comprising: a left hand power valve arrangement contained within the body having a left hand first balance chamber, and a right hand power valve arrangement having a right hand first balance chamber; a pressure port (50,50') contained within the body; a left hand spool assembly contained within the left hand power valve arrangement operable by an operator for selectively placing the pressure port into fluid communication with a left hand brake port, and a right hand spool assembly contained within the right hand power arrangement operable by an operator for selectively placing the pressure port into fluid communication with a right hand brake port; and the left hand brake port contained within the body in fluid communication with the left hand first balance chamber, and the right hand brake port contained within the body in fluid communication with the right hand first balance chamber; and a balance valve arrangement contained within the body having a second balance chamber, a left hand balance valve (60, 62, 64A, 64B) that places the left hand first balance chamber into fluid communication with the second balance chamber when the pressure in the left hand first balance chamber exceeds a predetermined value and hydraulically isolates the left hand first balance chamber from the second balance chamber when the pressure in the left hand first balance chamber is less than the predetermined value, and a right hand balance valve that places the right hand first balance chamber into fluid communication with the second balance chamber when the pressure in the right hand first balance chamber exceeds a predetermined value and hydraulically isolates the right hand first balance chamber from the second balance chamber when the pressure in the right hand first balance chamber is less than the predetermined value. a left hand power valve arrangement contained within the body having a left hand first balance chamber, and a right hand power valve arrangement having a right hand first balance chamber; a pressure port (50,50') contained within the body; a left hand spool assembly contained within the left hand power valve arrangement operable by an operator for selectively placing the pressure port into fluid communication with a left hand brake port, and a right hand spool assembly contained within the right hand power arrangement operable by an operator for selectively placing the pressure port into fluid communication with a right hand brake port; and the left hand brake port contained within the body in fluid communication with the left hand first balance chamber, and the right hand brake port contained within the body in fluid communication with the right hand first balance chamber; and a balance valve arrangement contained within the body having a second balance chamber, a left hand balance valve (60, 62, 64A, 64B) that places the left hand first balance chamber into fluid communication with the second balance chamber when the pressure in the left hand first balance chamber exceeds a predetermined value and hydraulically isolates the left hand first balance chamber from the second balance chamber when the pressure in the left hand first balance chamber is less than the predetermined value, and a right hand balance valve that places the right hand first balance chamber into fluid communication with the second balance chamber when the pressure in the right hand first balance chamber exceeds a predetermined value and hydraulically isolates the right hand first balance chamber from the second balance chamber when the pressure in the right hand first balance chamber is less than the predetermined value.