Hello

looking for some input on the problem I am having with my back brakes. Everything has been replaced with new parts MC, lines, brake cylinders, pads, springs etc. I have the brakes set up as to manual specs. and have good hard pedal with about 1 1/2 - 2" of free movement at the top. The problem I am having is about after 20 minutes of driving I lose my free pedal, pedal hard right at the top with no free play and my back brakes are starting to lock up and wheel hubs are getting hot. So I re a just the pads so wheel turns freely and after they cool down the pedal goes back to having free play again, take it for another drive and does the same thing, I've done this about 3 time's now what am I missing do the pad's expand or are the cylinder's not working properly ? must admit this is my first brake job thanks for any suggestion's