In this paper, dynamic behavior of rail vehicles during curve negotiation when traction or brake torque is applied has been studied. Vehicles with conventional symmetric trucks are compared to those with the recently proposed trucks having longitudinally unsymmetric suspension characteristics. Computer simulations using full car body models considering non-linear characteristics of the contact force between wheel and rail are performed. Wheel lateral displacement and wheel attack angle are calculated to describe curving performance under different speed, curve radius, and vehicle load. Under the same curve conditions, wheel lateral displacement is considerably smaller and wheel attack angle is almost zero within wide range of torque, while growing from higher value in case of conventional truck design. Consequently, enhanced curving performance of new unsymmetric trucks even under acting traction/braking torque is proved.