**6. Ride comfort**

To provide ride comfort to passenger, leaf spring has to be designed in such a way that its natural frequency is maintained to avoid resonant condition with respect to road frequency. The road irregularities usually have the maximum frequency of 12 Hz(Yu&Kim,1988). Therefore, leaf spring should be designed to have a natural frequency, which is away from 12 Hz to avoid the resonance. Stiffness is more and weight is lower of CLS than that of SLS. Therefore, first natural frequency of CLS (14.3 Hz) will be higher (126.98%) than that of SLS (6.3 Hz). First natural frequency of CLS is nearly 1.2 times the maximum road frequency and therefore resonance will not occur, and it provides improved ride comfort. After optimization, CLS has a fundamental natural frequency of 41.5 Hz, which is 3.46 times the maximum road frequency, which ensures that resonance will not occur.
