Are your rear shoes any good? It amazes me how they sell all kinds of high end front pads, then they sell crap rear shoes, then try to justify it by saying , oh well, the fronts do most of the stopping. If you shop around and get the commercial duty rear shoes, it makes a huge difference ( it also costs a bundle) The standard duty shoes fade WAY too easily and , as mentioned, if you have any old hose, it can balloon out under high pressure. It cost a fortune, but if you can afford it, braided steel brake lines work best with high pressure systems.