I spotted this on the Suzuki stand at Geneva. It’s the rear axle of the Vitara, the Hungarian-built Poor Girl’s Evoque.
At first I thought that it was a De Dion axle, on closer examination it turns out to be a torsion beam with driven rear wheels. Possibly other manufacturers have done this before, but it’s the first I’ve encountered. I’d have expected to find a live axle, or a multi-link or double wishbone fully independent system.
If Suzuki deserve credit, then it’s a neat solution. Wheel travel looks limited, given the short trailing arms, but all the virtues of the torsion beam are there – semi-independent operation, a degree of side to side interconnection, and no need for complex and expensive bearings and links. The set up looks cheap to make and easy to install on the assembly line, with the further benefit of easy compatibility with the front wheel drive versions.
De Dion axles are still around, the Smart and Twingo feature them, but they only make sense with a rear mounted engine or transaxle. They’re not really a halfway house to full independence. The axle is still solid, with the rear wheels constantly parallel to each other. The only real advantage is reducing unsprung weight, more so with inboard brakes, as featured on the Rover P6.
Driven To Write 
Is that a unique solution built for the Vitara, or have Suzuki just taken a torsion beam set-up off one of their front drivers and added a diff and driveshafts, in which case it suggests more parsimony than imagination?
And the Caterham uses a De Dion set up though, as a front-engined, rear driver, its requirements are different from the average BMW. The Lotus Seven was designed with a live rear axle, so the De Dion was cost effective. Also, since the car is light, it;’s presumably better at keeping the wheels planted under acceleration than a true independent set-up.
I hope we’ll do a De Dion piece this month. It always ended up on some of the more interesting cars of the 60s and early 70s.
This recent flurry of articles looking under the car has been informative. De Dion is a name that makes me think Rover P6 which leads to the regressive SD1 series with its live beam axle. But as I said elsewhere, it’s the tuning that matters and the live axle did the job with fewer bits than Ford or Vauxhall’s solutions.
I’ve just refreshed my memory of De Dion axled cars with a quick look at Wikipedia. Apart from the usual suspects, comprising a large number of low production run large GT cars, I see the original Nissan/Prince Gloria used one.
On the P6 matter, it’s reported in James Taylor’s book that in a 1969 Autocar interview, Peter Wilks had said that his uncle Maurice was “dead against” the De Dion axle proposed for the P6. The P6 design team believed that the £35 additional cost over a live axle was “well worth it just to write De Dion in the specification of the car, even if it hadn’t turned out to be any better. We did in fact succeed in creating an image of engineering innovation which had an impact which the car might otherwise not have had”.
Such was the thinking at the time. If Maurice Wilks had prevailed, P6 owner s might have been spared the misery of seized sliding joints and oiled-up inboard rear brakes, but the glory of the car would have been somehow lessened.
This focus on oily bits is welcome. We all have an opinion on design, but all I know about suspension systems is taken on trust from people with a lot more expertise than me.
The Vitara is a decent car, no? Unlike the Evoque, it is commendably light, which removes one of the main drawbacks of SUVs. It makes it a credible urban vehicle, as it can be reasonably efficient without resorting to a dirty diesel powerplant.
The relatively new Mazda CX-3 AWD sold in Canada has a very similar type of torsion beam rear supension set up with the driveshaft from the front coming pretty close to the beam. Looks as though the FWD model rear suspension bits are identical so designed thay way from the start. A bit cheap and nasty to gaze at, that suspension, but the silly thing actually handles extremely well. Some of the money they saved from a true IRS seems to have gone into a few nice trim bits in the cabin.