MAD auxiliary springs are progressive-rate helical steel coil springs fitted in unison with the original suspension. MAD Progressive remains passive while the vehicle is unladen, with little or no effect on the ride or handling or on the normal response of the suspension. Where space or the design do not permit an additional spring, a complete replacement main-spring is fitted with the same improved characteristics. As the load imposed on the suspension increases, the springs gradually become stiffer, reducing the amount of suspension deflection and maintaining a more level attitude in relation to the road surface. This, in turn, enhances ride comfort and safety and helps to reduce wear and tear on factory fitted suspension components.