Abstract: A universal crossmember assembly is provided for a motor vehicle having a roof and first and second rails attached to the roof. The assembly includes a crossbar having first and second ends along an axis. The assembly further includes a first clamp mechanism engaged with the first end for securing the crossbar to the first rail. The assembly further includes a second clamp mechanism engaged with the second end for securing the crossbar to the second rail. Each clamp mechanism includes at least first and second jaws having an associated one of first and second rail gripping surfaces for gripping one of the rails when an actuator is moved to an actuated position. Each clamp mechanism further includes a biasing mechanism capable of urging the first jaw away from the second jaw when the actuator is moved to a non-actuated position.