I've replaced my front brakes twice within the lat 6 months and my rotors once. I just bought new calipers, rotors, and brake pads today to replace them. I was told my front calipers are not releasing causing them to constantly rub and wear down faster. I also think my rear brakes aren't working because they pads and rotors look brand new almost. I use a trailer for work so 4-5 days a week I'm pulling a trailer about 6-7 hours a day. I've tried bleeding the brakes before and it doesn't seem to help. What could be causing the rear brakes to not engage?