what are you talking about? just replace the brake pads, yeah the rear pads are tiny compared to the front pads....if a caliper piston is locked and not retracting that could burn a pad real quick. Just be sure what is going on before you proceed with a repair. I doubt it's a swollen brake line..could be a locked caliper though...you'll find out quick enough when you try to retract the piston back into the caliper to make room for the new brake pad....good luck