Suspending his disbelief, Driven to Write asks whether Citroen’s claims for their Advanced Comfort® programme are worth their weight in hydraulic fluid.
Last October, Citroën announced a heavily revised C4 Cactus, intended not only to boost the fortunes of the established (and fading) model, but also to replace the moribund C4 hatch. As we know, in so doing, Citroën abandoned the original car’s distinctive and pleasingly unaggressive style, reverting to a less polarising, yet also more generic look. More grown-up, as the gentlemen of the press might put it.
Views on the car’s visual transformation have already been stated and are not the subject of today’s enquiry. The roll-out of Citroën’s new comfort-biased suspension however is. Announcing it in a press release last October, PSA said; “Benefiting from the Citroën Advanced Comfort® programme, the New C4 Cactus is the first model in Europe to feature the suspension with Progressive Hydraulic Cushions™ (PHC), making the ‘magic carpet ride’ effect accessible to the greatest number.”
All of which sounds promising on paper, but every automotive press release promises the sun, moon and stars on a glittery stick, so what does it amount to in practice? Here’s Citroën’s press department again.
A EUROPEAN FIRST: SUSPENSION WITH PROGRESSIVE HYDRAULIC CUSHIONS ™ (PHC)
The New C4 Cactus is the first model in Europe to be equipped with the suspension with Progressive Hydraulic Cushions™ (PHC), a Citroën innovation set for roll-out on future range vehicles. Citroën’s expertise in suspension is undisputed. For 98 years, suspension comfort has been embedded in the Brand’s genes. And over the years, customers have grown attached to Citroën’s comfort, which is unique on the market. Drawing on its expertise and the know-how of its engineers, Citroën developed the new suspension system to improve the filtering quality typical of Citroën and so dear to its customers.
Some 20 patents were filed in the development of the new suspension. The way it works is quite simple. While conventional suspension systems comprise a shock absorber, a spring and a mechanical stop, the Progressive Hydraulic Cushions™ (PHC) system adds two hydraulic stops on either side, one for compression, the other for decompression. The suspension therefore works in two stages to match how the car is used.
For light compression and decompression, the spring and shock absorber control vertical movements together with no assistance required from the hydraulic stops. But these stops gave engineers greater freedom in the car’s clearance, providing a ‘magic carpet ride’ effect giving the impression that the car is gliding over uneven ground.
During major impacts, the spring and shock absorber work together with the hydraulic compression or decompression stops, which gradually slow the movement to avoid jerks at the end of the range. Unlike a traditional mechanical stop, which absorbs energy but returns a part of it, the hydraulic stop absorbs and dissipates this energy. This means there is no bouncing.
With this innovative technical solution, the New C4 Cactus brings motorists peerless comfort and a ‘magic carpet ride’ while taking nothing away from handling and driving pleasure.”
This sounds rather simple, largely because it is. What it essentially seems to add up to is the addition of an assist and rebound spring within the existing damper assembly. This is not to dismiss the work of Citroën’s engineers, but it’s a long way from the sophistication of their now-discontinued oleopneumatic system. While some would suggest that this is no great loss, given its alleged complexity, propensity for expensive repairs and hydraulic power losses, speaking with those who know and understand the system refutes this somewhat misinformed view.
The original oleopneumatic sytem as applied to the 1955 DS was designed and made to aviation tolerances, it’s believed, because to do otherwise would simply have prevented it from working at all. Similarly, I’m reliably informed the power losses through the engine-driven hydraulic system were minimal and likely compensated by the weight saved from the deletion of conventional springs and dampers, to say nothing of the benefits to steering, handling, attitude, ride and stability at speed.
Hydropneumatic’s biggest enemy was its apparent complexity. Few understood its advantages and these were never properly sold to the public. Once PSA took over in 1975, the system was progressively starved of investment and over time both cheapened and neutered. By the time the plug was pulled, it was easy (and convenient) to dismiss it as yesterday’s technology. But what’s gone is gone.
Not so long ago, the announcement of new suspension technology from Vélizy would have been greeted with both jubilation and serious technical analyses, so the lack of either from the UK-biased press is either deeply puzzling or rather telling, depending on which side of the fence you sit. What it does suggest is either a disdain for the principles involved, or an element of cynicism, suggesting an innovation that amounts to little more than some trick dampers.
Yet, in separate articles last year, both Autocar and Top Gear sampled a prototype fitted with the new-generation damping system and ‘Advanced Comfort’ seats. Autocar’s Steve Cropley provided his expected gushing eulogy, while Top Gear’s Ollie Kew, (late of Car, but TG really is his natural habitat), offered the following. [Warning: the following contains a style of writing some DTW readers may find distressing]
“On the move, this Cactus is just uncanny. The ride is so good, it messes with your head – because this isn’t a luxury limo. It doesn’t have a football pitch-sized wheelbase or air suspension. It’s a flipping supermini, but it’s quashing bumps – genuinely vicious, craggy knolls and gnarly surfaces – like the lovechild of a WRC racer and a Rolls-Royce Phantom. It’s freakish, and all the more exciting because there’s no electronic voodoo or million-quid gadgets making it happen. Just some extra adhesive, elegant suspension, and squidgy cushions.
Oh, and it’s not just the ride. The steering is more linear, clearer too. Cars that ride cleverly tend to steer rather nicely, and this proves the point.”
QED then? Well, not quite. Firstly, know that young Mr. Kew (who looks barely out of short trousers) has no mental database of what constitutes ‘good ride’, because the last time car manufacturers gave the matter serious consideration, Ollie himself existed purely in the conceptual realm.
Secondly, let me say I’m incredulous that PSA have pursued this programme, given the level of disinterest that exists amid the tastemakers and more broadly, the buying public. What does it say that they are prepared to risk the expense, when nobody else in the so-called mainstream appears bothered?
It also suggests a surprising level of commitment to the double chevron from PSA despite a good deal of high-profile speculation to the contrary. After all, why sanction it (not forgetting a flagship saloon) if the plan was to run Citroën down?
But having got those caveats out of the way, it does not and never will compensate for the discredit and ultimate discontinuation of the hydropneumatic principle. Because no matter how well the Cactus may behave with this new damping system, it can only be viewed as oleopneumatics on the cheap.
Neither does it alter the universal truth that tyre sidewalls are now universally too stiff, of too low a profile, that wheel sizes are too large and both sprung and unsprung weight is too high for accuracy in steering or handling. (And that’s before we even get to issues of ride) The Cactus, being based on supermini hardware might benefit from being lighter than its C-segment rivals but still suffers similar handicaps.
What we appear to have then is a system, (not unlike Audi or Mercedes’ inordinately complex semi-active designs) that strives to overcome a set of demands dictated by an over-emphasis on initial turn-in and ultimate handling above all other parameters. It’s essentially a putative solution to a problem which ought not have arisen in the first place.
I hope it works – I genuinely do. Despite everything, I’d like Citroën to succeed with this because any commitment to ride comfort over ultimate handling is preferable to the stalemate that exists now. But a few diehard comfort-zealots aside, does anyone really care any more? That’s the question that is undoubtedly keeping Citroën’s chassis engineers like Nicolas Berlinger awake at night. He’s about to find out.