In this paper we present an experiment to measure the upper and lower thresholds of the Stimulus Onset Asynchrony (SOA) for continuous/discrete apparent haptic motion. We focus on three stimulation parameters: the burst duration, the SOA time, and the inter-actuator distance (between successive actuation points). The experimental setup is based on a set of six (6) vibrotactile actuators to investigate effects of the inter-actuator distance (over the range 4 cm to 20 cm) on the respective SOA thresholds. We found that as the burst duration increases, subjects detected the simultaneous-discrete boundary at lower SOA. Furthermore, the larger the inter-actuator distance, the more linear the relationship between the burst duration and the SOA timing. Finally, the large range between lower and upper thresholds for SOA can be utilized to create continuous movement stimulation on the skin at 'varying speeds'. The results are discussed in reference to designing a tactile interface for providing continuous haptic motion with a desired speed of continuous tactile stimulation.