My rear brakes are extremely hot after riding for 20 or so minutes. I have read that it's caused by the hose that attaches to the hard lines on the rear axle, is falling apart and debris is creating a vacuum. I have changed that hose out and have no problems bleeding the lines out easily. I have drum brakes all around and the fronts give me no problems. The truck doesn't have a proportioning valve off of the master cylinder, could that be the cause? This problem is infrequent as well which I find odd. Thanks for any help!