Four-wheel electromechanical braking (EMB) systems may receive nominal brake torque commands that exceed transient actuator capability under low-voltage supply or degradation. This study proposes a brake torque allocation method based on wheel-end dynamic reachable sets, defined here as one-step torque intervals permitted by voltage-dependent magnitude and application/release rate limits from the previous actual output. A single-wheel EMB model identifies the capability boundaries. Each interval is updated using the wheel’s bus voltage, capability coefficient, previous-cycle actual torque, and control period. Nominal commands are projected onto these intervals, and residual demand is redistributed according to the remaining margins. MATLAB/Simulink–CarSim simulations compare the method with fixed-ratio, static saturation, and dynamic-bound quadratic programming (QP-D) allocation. Under a synchronized 24 V supply, DRA reduces integrated brake demand deficit by 28.8% relative to the fixed QP-D benchmark. Under rear-left degradation, it reduces the peak yaw rate by 78.0% relative to static allocation. These results support capability-aware command allocation in the tested model. Strongly unequal voltages nevertheless produce the largest yaw response with DRA, identifying yaw-aware coordination as a necessary extension for this operating regime.