Could be either your pads are glazed or more likely the rubber brake lines have aged and are expanding when you step on the brakes. Joe Darlington offers some great braided stainless lines for our vehicles (covered in clear plastic) that made more difference on my brakes than new performance rotors and pads! Don't forget to order the brake bleeder valves that he offers that make brake bleeding a true one man job - they are one way valves that let air out when bleeding and then seal when you lift your foot.