Hope Springs

Suspending his disbelief, Driven to Write asks whether Citroen’s claims for their Advanced Comfort® programme are worth their weight in hydraulic fluid.

The face of convergence. Nu-Cactus. Image: Autocar

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.


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.

Image: robins and day

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.

Author: Eóin Doyle

Co-Founder. Editor. Content Provider.

15 thoughts on “Hope Springs”

  1. First on the “Nu Cactus”. Denuded of doors’ big crash barriers, it’ll lose its popularity in the hire market, where the value of avoiding door-to-wing dings is obvious, as it is in most car parks. Plus it’s now so bland as to be ignorable.

    The PHC seems quite crude. Maybe your TG man could, had he worn longer trousers, compared it with Skyhook, much appreciated by Maserati owners but scarcely noticed by Thesis drivers — perhaps a back-handed compliment.

    A relief to see PSA at least trying to reconnect Citroën to its illustrious past, even if this seems designed to reproduce the 2CV’s ability to cross fields without breaking the eggs.

    Yes, bigger wheels are playing havoc with unsprung weight, giving designers ridiculous challenges to keep the tyres in contact with the road. The steering challenge is separate and, as you say, is affected by tyre depth versus the quick-selling quick turn-in substituting for genuine feel. Increasing use of electronically controlled steering doesn’t seem to be coping well with this yet: will it ever?

  2. The way the motor industry now operates, I can’t help wondering if these new dampers have been developed by a damper company rather than PSA, especially when Citroën claim to have expertise in making great riding cars when this clearly isn’t the case or how would the DS5 exist? Having owned several hydropneumatic Citroëns in the past I can say it wasn’t the ride that I saw as the main advantage but more the unique feel and driving quality the system bestowed; the precise steering and unflappable way they dealt with scrappy roads along with the load carrying and safety advantages of self-levelling suspension.

    1. Vic: I was intending to conflate this with Skyhook, but approximately 1400 words in, I realised I was well out of the shallows (and well past my word count), so that will have to await another time. I’d like to look more closely into this whole area, so I may return to it at a later date. You’re right about the 2CV analogy. To some extent this seems an effort to address a more simplified past – none of that ‘Goddess nonsense’.

      Mark, I’d wholeheartedly agree with your point about the holistic benefits of oleopneumatics. It’s simplistic to confine its appeal simply to ride comfort. The CX’s I became familiar with (in particular) were characterised by a sense of utter indomitability in all conditions. I never felt as actively safe or more in control in a car.

    2. Hyrdopneumatic Citroëns certainly did convey a sense of absolute superiority over the underlying road, regardless of surface.

      I remember cruising at a reasonable clip down some country roads here in the lower North Island, both driver and passenger feeling quite relaxed in the BX. Some “yoofs”were attempting to keep up with us, but having such a hard time keeping their vehicle under control I slowed down for fear of them crashing. Similarly on one of the motorways near the Dutch-Belgian border with a shockingly poor road surface with lots of large dips, I watched a CX motoring along far faster than any other vehicles, simply because it could. Watching the wheels track the road surface whilst the car remained so composed was almost hypnotic.

      Another story was from a tyre garage. I had to help the guy change tyres on a CX (he couldn’t work out how to get the rears off, nor extract his trolley jack…), and in return got to learn quite a few more swear words. He hated “stupid French cars” that were so difficult to work on. Give him a Holden or Ford Falcon any day. Much easier and quicker too. Or so he said until the owner took him on a trip up north in the CX and he got to drive it back down. The next time I caught up with him he was gushing in his praise of the “stupid French car” – the fastest, least stressful trip he’d ever made back from up north, so smooth, relaxing and “those brakes”!

      I really don’t get the current fascination for handling above all else (at least in anything other than sports cars). How often can you really exploit that last 20% of handling? Wouldn’t comfort coupled with secure roadholding be a better bet, and more use more of the time? Bloody Nurburgring has a lot to answer for 😉

      Let’s not even mention that vastly superior braking system…

  3. Citroen/PSA has announced a big push to come back to the USA. They’ve even picked an purchased a new US HQ (In Atlanta, GA)

    I’m not convinced they’re going to make it. Despite some very unique (for the US) styling, US clientele are generally uninterested in anything too visually exciting.

    1. PSA’s Carlos Tavares has kept his cards quite close to his lapel as to what PSA nameplate will be crossing the Atlantic. I’m prepared to place serious money on it not being Citroen. DS? Doubtful, given that the entire enterprise currently appears to hang on a knife-edge and will, one ardently hopes, slide quietly into the wastepaper basket from whence it came.

      I could see Peugeot making a return, there being some brand-recognition and some little residual affection for the name. But in my opinion, the best and most likely bet is Opel. If nothing else, it would lend some reason to the acquisition – one which I’m still struggling to see the sense of.

  4. At least Citroen are trying something in pursuit of genuine differentiation. They really need a better, up to date platform to work from, but that would require serious investment from above.

    The point about big wheels is a valid one. With their new design-savvy strategy, could Citroen not accept the challenge of making smaller wheels fashionable? Surely a Cactus would be much better with 16″ wheels and taller, narrower tyres?

  5. Some newer dampers over the last four years or so have “helper” coil springs above the piston to avoid a hard bottoming out/ crash through – gives a rising rate towards the end of upwards suspension travel. The new Accord has them in more expensive models and Toyota or Nissan does as well.

    So using hydraulic soft stops on both full bump and full droop seems like an eminently sensible idea. You can then use softer main springs for a better ride.

    As others say, you’re still dealing with oversized wheels and rubber band tires though. BMW could use actual working dampers on the rear of their 3 and 4 series cooking models. Not many of us enthusiasts often ride in the back – my trip in the back of a new 428 was a constant heaving through large suspension movements. Quite uncomfortable and not what I was expecting at all. The rock hard rear bench didn’t help.

    Crossovers like the Mazda CX-5/Honda CR-V/Toyota RAV4/Nissan Rogue don’t have these skinny sidewall tyres, and no doubt ride better because of that fact – 55 and 65 series tyres are the common fare, unless you decide to go full-bling on the upscale 19 and 20 inch wheel options and ruin things all by yourself.

  6. The Hydrolastic and latter Hydragas systems used by British Leyland were a less complex arrangement than the French Hydropneumatic system and by 1982 the system had reached its pinnacle being fitted to the Austin Ambassador of that year and comparing favourably with cars costing ten times as much. Hydragas was pensioned off in 1984 in favour of struts and springs for the Maestro and Montego simply because they are cheaper to make and more reliable for a family saloon. A great shame.

  7. My dad is on his third (all of them purchased brand new) hydropneumatic-equipped Citroën, a 2007 C5. His previous ones were a 1990 BX 1.4 kat and a 1999 Xantia 1.8i 16v – both supremely comfortable and astonishingly capable mile-eaters. The C5’s suspension is much harsher than its predecessors, but the incredibly soft seats and high-profile tires make up for it somewhat. At any rate, never mind the bollocks spewed by the fleet-buying bean counters who don’t know one end of a car from another: All our Citroëns so far have proven to be ridiculously reliable, with their suspensions only ever needing refills at the intervals you’d have changed your shock absorbers in a conventionally-sprung car. Have we ever replaced the spheres before selling any of these cars on to its next owner? Yes, but at around 180,000km. Bottom line: Don’t listen to the common myth – hydropneumatic is ridiculously reliable if your mechanic understands basic plumbing.

    1. I can say my own car´s hydrulics have been pretty good. I had a leak about fifteen years ago and I have not had one since. My outstanding issues are that the stabiliser keeps going on the fritz so that the car´s front suspension would not rise. And there´s a leak in the pinion valve on the steering column which I am told is fixable by having it reconditioned. No, not perfect. No, not at all what you´d call serious. Every systems fails in some way from time time unless the system is a 1 kilo block of gold.

    2. Don´t envy me too much. I hardly drive it at the moment. It needs some work which I keep putting off because I don´t strictly need a car at all. It is a fine car though. They have become really rare. It might be two years or more since I saw one where I live.

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