The radiator assembly for a liquid-cooled off-road motorcycle is generally attached to the side of the frame. Therefore, if the motorcycle topples over, the radiator may strike the ground and receive an impact through the plastic side cover. This may deform the radiator, reducing its cooling performance or leading to a coolant leak. The strength of the radiator and plastic side cover was designed so that the radiator assembly will not deform easily if the motorcycle topples over at low speeds. However, due to the complex behavior of the radiator assembly in strength tests, a degree of trial-and-error may be necessary to incorporate strength countermeasures by tests alone. Therefore, a strength test simulation method was developed to help design the required strength of radiator assemblies.