Dubonnet suspension was a system of trailing arm independent front suspension and steering popular mainly in the 1930s and 1940s. Not very durable unless exactingly maintained, it was soon replaced by other designs. It consisted of a rigidly mounted axle beam from which the sprung steering and suspension arms pivoted around kingpins mounted on the ends of the axle. The wheels themselves were mounted onto stub axles, suspended by self-contained suspension units outboard of the kingpins. The system featured an encased coil spring and shock absorber, which sealed in the oil needed to lubricate and protect the suspension parts. This was also the weakness of the layout, as any leaks would have negative effects on ride and durability.