Four link suspension

[Brad Grant]

I deal with a number of classes of motor sport that use solid axle rear suspenion systems with four trailing links and a watts linkage or panhard rod. I have read many books on the subject but none have ever fully explained how changing the pick up points on the diff or chasis or diff nose angle affects the load applied to the tyres. Obviously all books talk about anti-squat geometry and always express it in terms of a percentage from centre of gravity.
If anyone knows of a particularly good suspension engineering book on the subject or better still does knows exactly how it all works then please reply.

[KC]

From my experience racing RC cars, a four link system allows the adjustment of rear caster and anti-squat. These affect how quickly the weight transfer to the rear tires occurs. Four links are also used to limit wheel hop and axle misalignment during hard acceleration and cornering with very powerful engines. You might try checking out some drag racing suspensions and sprint car suspensions as four link setups are very common in Pro Stock drag cars and World of Outlaw sprint cars.

[Franklin]

"Obviously all books talk about anti-squat geometry and always express it in terms of a percentage from centre of gravity."

A degree of intentional squat is part of the function of four-link suspensions in Pro Stock and other drag cars.