What Is Double Wishbone Suspension, And Is It Superior?

Double wishbone suspension is a setup commonly found in high-end sports and supercars. We explain what it’s good – and not so good – for

When an exciting new sports car or supercar emerges, you might notice there’s talk of the vehicle having ‘double wishbone suspension’. You’ll probably know this is generally considered to be a rather good thing. But what the hell does it mean?

What is it, and why is it better than a MacPherson strut?

A double-wishbone setup is made up of two wishbone-shaped arms (hence the name and these are sometimes called ‘A-arms’) with one at the top and another at the bottom, with the damper attached to the latter.

It offers a vastly different geometry to a MacPherson setup, which features a control arm and radius rod joining the hub at the bottom, with the shock absorber protruding from the top.

As a result of its design, the more it’s compressed, the more negative camber is introduced thanks to the use of unequal-length control arms. As you’re cornering hard and the car starts to roll, a double wishbone suspension system will maintain a better tyre contact patch with the road.

You can achieve this by stiffening a MacPherson setup, but the advantage of the double-wishbone is you can have comparatively softer damping without compromising the contact patch. The result is a car that’s typically more comfortable and less nervous-feeling on bumpier roads.

As a more complex design, the double wishbone allows for greater control over camber, caster and roll centre. There’s also much more freedom with the placement of the dampers, leading to the trick inboard setups you’ll see on many racing cars and even some road-going supercars.

Finally, since the damper isn’t sticking out the top of the hub, this type of suspension is much more economical in terms of vertical space. You can still have a reasonable degree of suspension travel without having to raise the ride height, which negatively affects the handling by increasing the centre of gravity.

In terms of performance, double wishbone trumps MacPherson. So why aren’t more cars built this way?

The cons of double wishbone suspension

A big factor is cost. Where MacPherson is simple and cheap, double wishbone suspension is more expensive and more complex. The design and manufacture of a double wishbone setup is generally going to increase costs, which is why it’s usually relegated to pricier machinery where ultimate handling is a bigger priority. Plus with more joints to worry about, the owner is potentially going to be burdened with higher service costs relative to a MacPherson setup.

The next problem is the packaging. While this arrangement takes up less vertical space, it needs more horizontal room thanks to the location of the upper arm. You either eat into cabin space, widen the car, or do a bit of both.

As with most aspects of car design, it’s all about compromise. Double wishbone could be seen as the ideal suspension setup, but it’s not the best solution for every car. It’s not guaranteed to be seen in every sports car, either – for example, Porsche still uses the MacPherson strut in most of its cars and only started putting double wishbones in the 911 with the 992 GT3.