I was changing pads and the right side went fine. When I went to the left side and attempted to compress the piston, it shot fluid out of the dust seal and would not retract. (Not sure if that was my fault or not from not giving even pressure to the C-clamp to the piston, but probably.) My question is, these calipers only have 65K miles on them. The right side looks perfect. Do I really need to replace in pairs? I have always heard that you should, but I assumed that meant that you were replacing due to wear and tear on an old set.