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VAUXHALL Astra rear suspension was the subject of a recent analysis by tech-fest industry title Automotive Engineer.
Michael Harder is chassis development engineer of the Astra line – and said that pleasing all of the people all of the time led to him eschewing multilink setups.
Vauxhall thus stuck to a cheaper twist beam. But how to make it class competitive? Spend €20 on a Watts linkage. Which Harder duly did, despite nobody doing it on a production car before.
He prefers to call the twist beam a ‘compound crank’: they’re lovely, he says, because they’re simple, don’t take up much space, and are easy to work with. There is a fault, mind, admits Harder: put side forces in, and the axle ‘tends to rotate underneath the car, which creates lateral oversteer and deflection’.
In practice, this means the front of the car turns in first, with the rear responding after an elastic-like delay. Giving the impression of laggy oversteer.
You can fix it, says Harder, with stiffer bushes. Ah, but these are bad for both noise and road isolation. So, enter the Watts linkage. This means the bushes can be softer, as it absorbs an impressive 80 percent of all lateral loadings on the rear suspension. It also improves camber stiffness – making it ‘twice as good as any other car on the market’.
Throw in canny tricks elsewhere, such as rebound springs in the front struts, which helped him tune roll stiffness without affecting understeer or oversteer, and you’ve something more than class competitive. Still, though, at way less cost than the expense of multilink.
You know, this ‘ere twist beam could just twist my arm…