Leaf springs are generally mounted on large cars and trucks because of excellent load-carrying traits. Usually the leaf-spring setup comprises a series of flat steel leaves bolted together to form a single unit, which is named semi-elliptical leaf spring. Leaf spring is better than coil springs at transferring forces from the road to the frame. Weight of steel material and friction between leaves are the 2 main problems of leaf springs. Hence comes into being the design of parabolic spring. Its leaf is tapered in a parabolic way rather than a linear way as traditional leaf springs are. The shape of taper keeps the spring flexible, but able to carry the load of the vehicle. It owns obvious advantages against stock leaf springs. First the leaves are reduced to up to only one piece. Therefore the weight of the suspension could be lowered. And it is known that Unsprung weight affects ride quality much more than sprung weight. Meanwhile less leaves means less inter-friction. With the shape thicker in the middle and thinner on the ends the spring flexes easier and in a progressive manner. Yet it is capable of supporting at least the same load ratings as stock springs and some cases even more.