Farm tractors with suspended front axle: Anti-dive and anti-lift characteristics

In recent years, many farm tractors equipped with a suspended front axle have been presented on the market. Such farm tractors are prone (much more than conventional ones) to the pitch of the body during either braking or traction. Such body movement can be reduced by setting the proper anti-dive or anti-lift characteristics of the suspension. In this paper, the analytical mathematical relations governing the anti-dive and anti-lift characteristic of the farm tractor are derived by considering both the common brake architecture and either the cases of two or four wheel drive systems. The effect of the very complex driveline of farm tractors on anti-dive and anti-lift characteristic is dealt with. It turns out that, to obtain an anti-dive behaviour, in case of four-wheel-drive, the non statically determined torque distribution between front and rear axles requires a proper tuning of the geometry of the front arms, particularly of their slope.