<p>This study proposes a rear-suspension-focused control strategy for pickup trucks subject to varying rear payloads. Two suspension systems—a fully active suspension and a semi-active magnetorheological (MR) damper system—are controlled using Linear Matrix Inequality (LMI)-based output-feedback controllers. A vehicle model developed through TruckSim and MATLAB/Simulink co-simulation is used, with actuation applied only to the rear suspension. A mass variation scenario is incorporated to estimate and adapt to shifts in the center of gravity caused by payload changes. Performance metrics such as pitch angle and longitudinal acceleration are analyzed to assess system effectiveness. Simulation results demonstrate that while the MR damper system reduces body oscillations within the limits of passive systems, the active suspension provides superior pitch suppression and vertical acceleration reduction. Notably, rear-only actuation still yields substantial improvements in ride comfort and handling. These findings underscore a practical and effective suspension control approach for commercial vehicles with variable loading conditions.</p>