The development of the conventional laminated leaf spring to the parabolic spring is illustrated in the figure.
The three springs considered here have the same length, spring rate and nominal load. The advantage of the parabolic spring, apart from the decrease of friction, is the decrease of the spring weight by around 50% (minimization of unsprung masses). The main advantage of the leaf spring is the combination of suspension and axle location, which is partially lost with the transition to parabolic springs with few leaves.