Panard rod, what is it?......

[Tony]

Despite the onslaught of front-wheel drive vehicles, some current and many classic two-wheel drive performance cars and trucks deliver power through a solid rear axle suspension. In this configuration, the ring-and-pinion, differential, and axles, brakes, wheels, and tyres are all components of the rear suspension, as their weight is supported by the springs. As the axle shafts turn, it’s sometimes referred to as a live rear axle. Conversely, a front upright is an example of a dead axle, where the wheels turn around the fixed spindle.

The axle assembly is attached, or ‘located’ to the chassis by various methods, traditionally by leaf spring as still seen on many pickup trucks. However, the most common method of attaching the rear axle assembly in modern cars is through the use of suspension links. These links control the axle’s movement in fore-and-aft and lateral movement relative to the chassis. The springs and dampers control the axle’s vertical movement. The geometry of these suspension links define the car’s rear suspension behaviour and overall handling characteristics.

Roll Centres

The roll centre of a suspension is the point around which the chassis rotates relative to the tyres. (The front and rear roll centres of a car’s suspension define the roll axis.) The roll centre describes how the cornering forces are divided up between the tires. Generally speaking, a lowering the rear roll centre moves the chassis balance toward understeer, while raising the rear roll centre moves the handling balance toward oversteer.

The roll centre height of a Panhard bar rear suspension is located at the link’s mid-point.  As the rear axle moves, the rear roll centre moves half as far. The Panhard bar can be attached to the chassis on either the left or right side. In theory, the side of the chassis to which the Panhard bar is attached can affect the way the car handles in left or right turns.

This example below displays exactly what happens when a Panard rod fails....