Wishbone Suspension System:

• The wishbone type is the most popular independent suspension system.
• It consists of two (occasionally parallel) wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle.
• The shock absorber and coil spring mount to the wishbones to control vertical movement.
• The vehicle weight is transmitted from the body and the cross member to the coil spring through which it goes to the lower wishbone member.
• The wishbones not only position the wheels and transmit the vehicle load but also rest acceleration, braking and cornering forces.
• The upper arms are shorter in length then the lower ones. This helps to keep the wheel track constant thereby avoiding the tyre scrub thus minimizing wear.

Objects of Suspensions:

• To prevent the road shocks from being transmitted to the vehicle components.
• To safeguard the occupants from road shocks.
• To preserve the stability of the vehicle in pitching or rolling while in motion.
• To provide required height to body structure as well as bear the torque and breaking reaction.
• To keep the body perfectly in level while travelling over the uneven road.

Construction:

• A telescopic shock absorber derives its name from tubular shape of early telescopes used in ancient times.
• They are 2 types viz. mono tube and twin tube type. The twin type shock absorber is as shown in the figure.
• Rod G is attached to a 2 way valve A; while another similar 2 way valve B is attached at the lower end of cylinder C.
• There is a fluid (oil) in the space between the valve A and B and also in the annular area between cylinder C and tube D.
• H is a gland in the head J. The eye E is connected to axle and eye F is connected to the chassis frame.

Working:

• Consider that the vehicle has come across a bump.
• Then the eye E would move up and thereby the fluid will pass from the lower side of valve assembly A to the upper side. But since the volume of the space above A is less by the volume of rod G, the fluid will also exert its pressure on valve assembly B and go to the underside of valve B.
• This passage of the fluid through valve opening provides the damping.
• A similar process takes place in opposite direction for rebound.