Abstract: A method optimizes trailer braking gain for a trailer that is towed behind a vehicle. The method receives an operator selected trailer gain. During a braking event, braking data from at least one sensor is received. Based on the received data and the selected trailer gain, an output trailer gain is provided. During the braking event, pressure in a master cylinder of a vehicle and an actual deceleration of the vehicle is monitored. The method determines if the actual deceleration is sufficient for the monitored master cylinder pressure and if not sufficient, the output trailer gain is automatically adjusted to provide an optimized trailer gain to brakes of the trailer until the actual deceleration of the vehicle matches an expected deceleration at the monitored pressure value.