Citroën’s secret new suspension system revealed

We’ve been highly critical of some Citroën and DS models in the recent past for not having a comfortable ride quality. The current DS 5 comes in for particular criticism in that regard at The Irish Times, but we knew that the company was working on a new suspension system which was promising a return to the glory days of Citroën comfort and softness.

Now, we’ve had our first peek at it. It’s the work of Citroën’s in-house advanced engineering team, working under the banner of ‘Advanced Comfort’. The Advanced Comfort team doesn’t just work on suspension; cabin lighting, seats and connectivity also come under its remit, as Citroën reckons that all these factors have significant implications for comfort.

The new suspension setup is the first chance we’ve had to see the work being done, though. Unlike early predictions of a complex ‘active’ suspension system, this is a purely ‘passive’ setup, one that reacts as would any car’s springs and dampers to muffle the bumps and thumps coming up from the road. A more expensive ‘Active’ setup is likely still under development for top-spec DS models, but that version (already dubbed ‘revolutionary’ in absentia by DS executives) remains under wraps.

What we have here is a normal spring-and-damper system, installed in a prototype C4 Cactus, but with the traditional sold ‘bump-stops’ that control the suspension’s movement in large impacts, replaced by a hydraulic ‘cushion.’ That cushion’s job is two-fold - on normal, small bumps it allows the suspension more freedom of movement, with the spring and damper working together but separately to control the car’s motions. On bigger impacts, the spring and damper work as one, slowing down the suspension’s movement and reducing the impact to the cabin of the car. The hydraulic cushion also means that if the full movement of the suspension is needed, the final impact into the bump-stop is slower, better controlled and the impact is dissipated out rather than being transmitted into the car’s structure.

That structure is also key to the new suspension’s workings - it’s 20 per cent stiffer thanks to the use of adhesive bonding between chassis panels (much in the mould of Lotus or Aston Martin) with spot-welding at any potential weak points. Citroën claims that this allows for a much stiffer structure with no weight penalty.

Interestingly, there’s also very little cost penalty in the system. The last versions of Citroën’s old ‘magic carpet’ hydragas suspension system were limited to top-end models, and larger ones at that. Family hatchbacks and the like had to go without. This new hydraulic cushion system has been costed, says Citroën, so that it can be applied to any model in the range, from a specced-up €35,000 C4 Grand Picasso all the way down to an €11,000 C1 city car.

New seats are also being designed, which use multiple layers of foam - firm, soft and ‘memory’ - to create chairs which support but which also offer the sort of squishy comfort we loved in classic Citroëns of the seventies and eighties. Citroën says that these seats are actually being inspired by the construction of beds…

“The Citroën Advanced Comfort Lab prototype features three innovations, one for each form of transmission, in order to reduce the vibrations felt by the occupants and thus significantly improve driving comfort. Citroën has filed more than thirty patents for the technologies implemented by this prototype, but they were all developed to be applicable, from both a cost and production standpoint, to all the vehicles in the Citroën range” said Citroën in a statement.