Tire Squeech

Lately when I make sudden hard braking, usually when someone in front made a sudden braking, that my tires instantly would make a loud screech sound. I wasn't sure if it was the rear or front brake that locked up and cause the tire to loss its traction, or if the tire itself have no grip when the sudden reduction of speed. I have the 1999 EX with Firestone tire and have 35k on it. Has anyone with similar problem? Is it time for me to change a better tire? or that the rear of the van was too light?


Richard