Weissach axle suspension

In mid-70's, Porsche developed this unique rear suspension for its award-winning 928. Basically it is a variant of  semi-trailing arm suspension.

In any suspensions, the pivot joints must be inserted with rubber bushing to absorb noise and vibration. For conventional semi-trailing arm suspension ( first row in the following picture ), when under braking, the momentum of the car body tries to pull the car "away" from the rear suspension. Due to the elasticity of the rubber bushing, the rear wheel will toe-out. As a result, the car will oversteer.

Weissach axle was designed to eliminate this oversteer ( second row in the picture ). By splitting one trailing link into two pieces, with a pivot jointing them, the oversteer under brake can be eliminated or even introduce some understeer ! This help stabilize the cornering motion. Some people call it as "passive rear-wheel steering".



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