This article investigates the effect of a decrease in the speed limit for motor vehicles on bicycle commuting in French cities. I use a difference-in-differences event study design to measure a possible causal effect of motor vehicle speed limits on changes in bicycle traffic. I do not find any effect of the reduction of the speed limit from 50 km/h to 30 km/h on bicycle commuting. This result is important for public policy design, since increasing the number of bicycles is one of the benefits that politicians expect from decreasing the speed limit for motor vehicles.