I’d no sooner finished writing A Disappearing Suspension Technology than I came across something that goes a long way to explaining the reason that swing-arm suspension was used by such hugely respected engineers like Porsche and by companies like Mercedes.

The magazine article is on a very interesting car produced by one of the all-time greats in suspension theory. The designer of the car was Bill Milliken and the premise was that by using narrow tyres running a huge amount of negative camber, very good cornering grip would be able to be obtained.

Now there’s a lot more to his car than just that (by clicking on the magnifying glass you can enlarge the article scans enough to print/read them) but the narrow tyres/huge neg camber is a very short summary.

The tyres being used by Auto Union and Mercedes pre-WWII race cars were similar in width to current big motorcycle tyres and so would have been far less susceptible to loss of grip through lifting of the flat tread of the tyre that would otherwise occur through negative camber. In fact, the lateral thrust from the camber achieved by the swing-arms would, as the Milliken car shows, have made a major contribution to cornering grip.

It makes me think that a lightweight car running low pivot point swing-arm (or semi-trailing or leading) suspension and motorcycle tyres could develop a lot of grip while maintaining an ultra lightweight suspension, in turn giving a very low unsprung weight and low total vehicle mass. And the narrow wheels and tyres would also give far lower rotating inertia, improving acceleration and braking still further…

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The other month I found myself commuting 160 kilometres each day, most of that on two, three and four lane freeways. When everyone’s travelling at basically the same speed, it’s an ideal opportunity to look at the suspension behaviour of other cars. For several kilometres of bumps, you can literally eyeball from close quarters the front or rear wheels of a car travelling at 100 km/h.

One of the interesting things is watching the front dynamic camber variations. Theory says that you want a neg camber increase in bump, primarily to keep the outside, loaded tyre closer to vertical as the car rolls. But theory also says that this dynamic camber increase is pretty well impossible to achieve with MacPherson strut suspension, unless the steering axis inclination is radical (which in turn brings other problems).

And can’t you just see it in action when you watch adjoining cars!

On my local roads, the (pre VE) Commodores and nearly all Japanese and European small cars have front wheels that just move up and down. But watch a Falcon, or any of the European cars with double wishbones, and you can see clear dynamic camber variations.

And the same thing applies at the back, except this time the wheels just moving up and down are those connecting to torsion beam rear axles (FWD cars) or solid rear axles (RWD cars). On cars with multi-link or wishbone suspensions, the camber change is quite obvious to the eye. Of course I’m not talking about much variation – perhaps a few degrees. But you can still see it.

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