The average replication rate at each tension (Vmean(f)) was determined by a line fit to the traces showing the number of replicated nucleotides versus time. The final average rate at each tension was obtained by averaging over all of the traces taken within similar tension values (±0.5 pN). Average replication rate without pauses at each tension (pause-free velocity, V(f)) was determined with an algorithm that computes the instantaneous velocities of the trajectory, averaging the position of the holoenzyme along the DNA over sliding time windows, as described previously (8 (link)). Tension dependent pause-free velocities were fitted to the strand displacement model described in SI and (52 (link)).