The crewed lunar vehicle (CLV) is an essential equipment for crewed lunar landing, as its mobility significantly expands the astronauts’ exploration range. Studying the wheel–terrain interaction through experimental methods has become the current research trend in the design of CLVs. This study investigates the wheel–terrain mechanical properties of CLVs under high-speed and heavy-load conditions. A wheel–terrain mechanics testbed for CLVs is developed. Using this testbed, experiments are conducted by controlling a wheel under varying loads (500–3000 N), angular velocities (0.5–3 rad/s), and slip ratios (0–0.6). Data on wheel–terrain interaction parameters (drawbar pull, wheel sinkage, and driving resistance moment) are collected for analysis. The results reveal that traction performance decreases with increasing velocity, and initially increases then decreases with increasing load. Finally, based on the experimental data, the conventional semi-empirical model of wheel–terrain mechanics is revised. The prediction accuracies of the revised model for driving resistance moment, wheel sinkage, and drawbar pull are 15.9%, 12.9%, and 26.7%, respectively, showing significant improvements over conventional models.