I have a 1997 ES 300 with brake shudder. I have replaced the rotors twice. The problem reappears soon after replacing the rotors e.g. within 5,000 miles. The most recent set of rotors that came off had a black scortch mark on the inside. The local auto place suggested I replace the calipers, rotors and pads with genuine lexus parts rather than aftermarket. The shudder almost seems like the antilock brakes are kicking in. Any suggestions would be helpful.