Two years after all new brakes, my brakes are very week. The fronts still look great. The rears are toast. So now I insatalled new rear rotors, calipers and pads, and thoroughly bled. The brakes are still very week. You cant lock them up, and it takes a ton of pressure to stop. The fronts do seem to be working when the car is jacked up, so why did the rears wear so fast and, why are the brakes still so week? Master cylinder? Proportioning valve? Also the ABS antilock light comes on and my parking brake cable is bad, but that doesnt seem to be related. Please help.

Two years after all new brakes, my brakes are very week. The fronts still look great. The rears are toast. So now I insatalled new rear rotors, calipers and pads, and thoroughly bled. The brakes are still very week. You cant lock them up, and it takes a ton of pressure to stop. The fronts do seem to be working when the car is jacked up, so why did the rears wear so fast and, why are the brakes still so week? Master cylinder? Proportioning valve? Also the ABS antilock light comes on and my parking brake cable is bad, but that doesnt seem to be related. Please help.

i would start by finding out your abs thing first
i do believe that the abs control unit controls or partly controls the pressure for the brakes

could also be what you stated master cylinder p- valve
check into your abs thing first

you shouldn't be able to lock up abs brakes
that is abs stands for anti lock braking system