Generally, when you feel a pulsating while braking, it is usually due to warped rotors. Whether it's front or rear, depends on where you feel it. Front, in the steering wheel. Rear, in the seat. But having drums/shoes on the rear, that might not be an issue. I'd suspect the fronts and here's why. Measuring with a mic won't give you the whole story. The rotors may still be warped. The mic measurements won't tell you if the entire rotor itself is warped, only if the thickness is different in areas around the rotor. Having them turned could be an option, but the price of rotors nowadays, turning them is steadily becoming nonexistent. Most often people buy new rotors if in doubt. Turning a rotor may cost 15 bucks each, while a new rotor may be 30 each for new, so it's really up to you. I'd bet the fronts are warped.