Minimum safety thickness for front rotors lexus IS 350 2006

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I had the vehicle serviced at a Lexus dealer because of extreme noise when applying the brakes. After checking the brakes technician stated brake fluid needed to be replaced and no further brake work was required. According to the dealer the measurements were 27.4 on the left front rotor and 27.5 on the right front. A couple of days later i take the vehicle to another Lexus dealer because of the same noise. They said vehicle needed new rotors, pads and shims and that the minimum safety thickness for lexus rotors is 27mm. Should they had replaced the rotors at the first Lexus dealer.