A method for controlling the speed of a motor for a tape drive in a mailing machine includes providing an optical sensor for signaling the appearance of slots in a slotted wheel connected to the motor shaft. The time intervals between slots are used to make a prediction in respect of expected future time intervals and the motor speed is adjusted in accordance with the predicted value to obtain the desired value. For best results, the data is received at the microprocessor using the "capture" mode of operation in order to avoid excessive errors due to a "busy" processor. The invention enables the small motor of a tape drive to avoid over and undershoot even when operating under highly variable load conditions.