Shake down

From K&C to seven-post, there’s a wide range of test rigs now available for checking, testing and developing motorsport suspension systems. Here’s Racecar’s guide to all you need to know about these extraordinary machines

- JAHEE CAMPBELL-BRENNAN

The role of a racecar’s suspension is a complex one, and includes control of wheel orientation, deflection, how accelerations are transmitted into the vehicle body and also the effectiveness of the overall aerodynamic package.

Usually, open-wheelers, prototypes and GT racers utilise a double wishbone arrangement, whereas saloon, touring and WRC-style cars often run a MacPherson strut at the front axle.

Compliance and flex

Double wishbone systems often have chassis-mounted spring-damper units, which must include a linkage to enable their actuation. This additional structural member is known as a pushrod (loaded in compression in bump travel) or pull rod (loaded in tension in bump travel). The pushrod/pull rod actuates a component known as a bell crank, which pivots around a fulcrum to exert a force on the damper. Running through the load path from the wheel upright to the damper in this inboard arrangement there is an array of bearings, fasteners and joints the force must journey through. These components help designers to tune the inherent compliance and flex of such a system and its influence on the kinematics.