The Insurance Institute for Highway Safety (IIHS) evaluates autonomous emergency braking (AEB) systems as part of its front crash prevention (FCP) ratings. To prepare the test vehicles' brakes, each vehicle must have 200 miles on the odometer and be subjected to the abbreviated brake burnish procedure of Federal Motor Vehicle Safety Standard (FMVSS) 126. Other organizations conducting AEB testing follow the more extensive burnishing procedure described in FMVSS 135; Light Vehicle Brake Systems. This study compares the effects on AEB performance of the two burnishing procedures using seven 2014 model year vehicles.Six of the vehicles achieved maximum AEB speed reductions after 60 or fewer FMVSS 135 stops. After braking performance stabilized, the Mercedes ML350, BMW 328i, and Volvo S80 showed increased speed reductions compared with stops using brand new brake components. The Acura RLX and Cadillac CTS showed no change in speed reductions, and the speed reductions of the Dodge Durango and Lexus IS 250 worsened.After the FMVSS 135 burnishing was complete, AEB runs at 20 and 40 km/h were conducted to compare the results from the original IIHS FCP rating tests. For each of the vehicles, the IIHS FCP rating was not changed by different burnishing procedures.Results show that AEB speed reductions can improve or degrade as new brakes progress through the FMVSS 135 burnishing cycle. However, the differences in either direction are small and none of the tested vehicles had speed reduction differences that were great enough to change the IIHS FCP ratings.