Citroen Hydropneumatique 1954 - 2018 +++ An attempt at a tribute thread +++ Caution: André's Asylum inside!

[Cleon-Fonte]

Torsion bars aren't torsion beams, though.

[DSdriver]

I know nothing about moderns

[Sigmund Fraud]

I know nothing about moderns

 

Sorry but 1974 isn't modern, even by Junkman's criteria : 

 

 

[Cleon-Fonte]

Wonderful video!

 

The P6 with roll control was oversteering a lot - I wonder if the project was canned because of fears that poor drivers would, bereft of the clues from roll, run out of rear grip at a point way past their ability to catch it?

 

Much less of an issue with a front drive / understeer car.

 

You'd be surprised how tantalisingly close Rover's hydropneumatics came to production. The Rover P8 - which was originally conceived as a single replacement for the P5 and P6 but later grew into a Jag MkX/XJ competitor - had the system from the get go, but after the creation of BL William Lyons used his place on the board to veto the P8 out of existence just as Rover was about to tool up for production.

 

Before the P8 was canned Rover realised they'd need a P6 replacement and inagurated another new car, the P10. Again, Rover's early product planning shows this originally was to feature their hydropneumatics, but by the time it came to actually engineering the suspension Rover had been subsumed into BL's Specialist Division and the cost accountants running the show made it clear, in no uncertain terms, that there wouldn't even be the money available for independent rear suspension, let alone weird hydraulics. When the P10 eventually appeared (as the SD1) it thus featured Macpherson struts and a very well designed live rear axle, albeit Spen King had managed to force through self-levelling dampers on the more expensive models.

[Junkman]

Sorry but 1974 isn't modern, even by Junkman's criteria

 

Yes it is.

Pretty much everything launched since the mid Sixties is a modern car.

Such is the lack of progress.

[Sigmund Fraud]

Yes it is.

Pretty much everything launched since the mid Sixties is a modern car.

Such is the lack of progress.

 

I stand corrected !

[Cleon-Fonte]

I know nothing about moderns

 

Effectively a torsion bar is a type of spring, originally invented by Citroen funnily enough, but beloved by the French motor industry since.

 

A torsion beam on the other hand is, as its name suggests, merely a coil sprung beam axle which can twist slightly along its length to provide the wheels with a limited amount of independent movement. Its primary advantages are cost related, which is why the modern motor industry uses them on just about anything it can get away with. This is despite them being almost universally shit.

 

One of the reasons modern French suspension is so terrible is that they traded the former for the latter.

[New POD]

I stand corrected !

 

You should sit.  Have a beer. I think what he's saying is that Not very much that's been invented to make cars better since 1974, was really worth inventing.  

[forddeliveryboy]

I believe a lot of the arguments, objections and mud-slinging the moment anyone dares point out the inherent advantages (laws of physics, not subjective opinion) of hydropn. suspension is a result of there not being a proper understanding of why it made it into mass production.

 

Reading the thread, there are comments about modern sphered Cits riding badly because of the adoption of the front strut (not true), that the company only did what they did because USP and they were capable (they did things differently if it could be demonstrated it was a better solution), McLaren are making use of the technology (no, their steel-sprung suspension deals with damping and anti roll, but was inspired by Citroën), that you can achieve as good a ride with conventional suspension (yes, but beyond a certain speed and loadings things deteriorate significantly compared with gas over oil) and so on.

 

It all comes down to one thing - by increasing the amount of time a tyre's contact patch pressure is optimum, effective suspension makes a car faster by increasing grip and stability, and not just through the suppleness an infinite rising rate and fully self-levelling setup allows. That's what Citroën was seeking and found - and achieved what nobody else has ever come close to, with such simplicity and effect.

[Tadhg Tiogar]

 

..... it's at speed on poorly surfaced roads with repeated large undulations where the system really comes into its own. ....

Viz. most non-autoroute French roads until the early 1980s...

....and increasingly many British roads in a piss-poor state of repair due to combination of no money and utility contractors deliberately digging up roads in order to put in their own shit patches. The kind of surfaces that may damage wheels or cause springs to fail.

 

I'm happy to have a CX: she is both my mistress and my midlife crisis. The itch that had to be scratched. If only I knew where all that Dexron III is going to, though.....

 

[Felly Magic]

Nobody has really brought the thorny issue of cost in to this, to make the systems in such low numbers nowadays must be hurting PSA financially, when they can just get off the shelf springs & dampers for a fraction of the cost. It had to face the axe when you actually think logically. Add in the often poor build, and vertical depreciation of big Cits, can you blame them for finally canning it? I can't to be honest

[RayMK]

Torsion bars aren't torsion beams, though.

 

Perhaps some of the confusion of terms comes from Peugeot who refer to the 205's rear suspension assembly as the rear beam. It incorporates two torsion bars - the beam merely acting as a non moving subframe for the trailing arm pivots and torsion bar fixed ends.  A torsion beam with its trailing arms of course provides wheel location, independant suspension and an anti roll function and thus has fewer components. Accountants love fewer components particularly when they can be made cheaply, hence McPherson struts also being common. Having owned a CX GTi Turbo 2 and a GSA for a while in the 1990s then gone back to conventionally suspended cars, I can also vouch for the fact that the they both made every road feel newly and expertly surfaced.  Most current 'moderns' have appalling suspension which only works as intended on very smooth roads. I would love a ride in a DS one day. 

[Tadhg Tiogar]

..... to make the systems in such low numbers nowadays must be hurting PSA financially, ....

 

What, low numbers like the 1.2 million CXs that were built at Aulnay?

[Talbot]

Just to add my twopenneth to this thread, I love Hydro Citroens. I haven't had one as a daily for a while now, and I miss them. I like the fact that they are hydraulically complex, that they are unconventional, and that their design aim was comfort and safe handling over a "sporty/dynamic" ride. They would be (and have proven to be) useless at being raced, and this is an good thing.

 

I also find the fully-powered brake system very confidence inspiring, and DIRAVI was just fantastic to drive with.

 

The DS, GS(A), CX and (most aspects of) BX showed this system at it's best. As soon as things like anti-sink, centre spheres, de-centralised brakes and conventional PAS were fitted, the system's days were numbered. I'm surprised it's lasted as long as it has, as in the 1960's and 1970's, car buyers were actually interested in the engineering in their cars, and things like the famous GS driving on 3 wheels or having a blow-out and steering dead-straight actually sold cars.

 

These days, most new car buyers don't even know how to open the bonnet, and couldn't care less about the underlying engineering of the car. Most couldn't tell you which wheels of their car are driven, or indeed how many cylinders their engine has, much less the details of it's suspension system.

 

A shame.

[Junkman]

Effectively a torsion bar is a type of spring, originally invented by Citroen funnily enough, but beloved by the French motor industry since.

 

A torsion beam on the other hand is, as its name suggests, merely a coil sprung beam axle which can twist slightly along its length to provide the wheels with a limited amount of independent movement. Its primary advantages are cost related, which is why the modern motor industry uses them on just about anything it can get away with. This is despite them being almost universally shit.

 

One of the reasons modern French suspension is so terrible is that they traded the former for the latter.

 

Ironically the Traction Avants had both, torsion bars and a torsion beam.

 

In addition, not a lot of people actually know that the 15-six could be had with hydropneumatic rear suspension in 1954 and 1955 (15CV-H), thus making it the first Citroen available with that system. Hence my thread title contains the year 1954, not 1955, the year most people believe the hydropneumatic suspension debuted with the DS.

[Zelandeth]

I'd love a shot of a CX, especially an early one.

 

Citroen have shown that there's massive potential in the system...the CX shows that from a comfort perspective - with the Xantia Activa firmer, but seeming to totally disregard any regard for physics where cornering is concerned.

 

It's something that has to be experienced to really be understood fully I think... getting into anything after the Activa these days feels like an ocean liner if taken around a corner of roundabout at anything over walking pace...

[forddeliveryboy]

Ironically the Traction Avants had both, torsion bars and a torsion beam.

 

In addition, not a lot of people actually know...

 

Is this a language thing? I'd describe a Traction as having trailing arms sprung by torsion bars with a beam between the wheels, with Panhard rod. In no way is the beam a torsion beam, it's a dead axle beam.

 

 

Just to add my twopenneth to this thread, I love Hydro Citroens. I haven't had one as a daily for a while now, and I miss them. I like the fact that they are hydraulically complex, that they are unconventional, and that their design aim was comfort and safe handling over a "sporty/dynamic" ride. They would be (and have proven to be) useless at being raced, and this is an good thing.

 

The design aim was to create a car which could maintain high speeds over roads with poor foundations and surfaces, something with a 'sporty/dynamic' ride would have been difficult or impossible to control without reducing speed.

 

The DS racked up plenty of rally wins through the sixties, perhaps surprisingly.

[Talbot]

The DS racked up plenty of rally wins through the sixties, perhaps surprisingly.

I should have been clearer.. I meant track racing. Rallying is a somewhat different matter, where soft long-travel suspension is much more useful.

 

There's a video somewhere of CXs being track raced. It's bloody hillarious to see them all leaning at near-2CV-angles while not really making much progress around the track.

 

One of the drivers realises the benefit of hydro though, and keeps cutting a corner by going over the grass, without reducing speed at all.

[Tadhg Tiogar]

.....There's a video somewhere of CXs being track raced. It's bloody hillarious to see them all leaning at near-2CV-angles while not really making much progress around the track.

 

One of the drivers realises the benefit of hydro though, and keeps cutting a corner by going over the grass, without reducing speed at all.

I'd like to see that video.

[forddeliveryboy]

There's a video somewhere of CXs being track raced. It's bloody hillarious to see them all leaning at near-2CV-angles while not really making much progress around the track.

 

They must have had a tight budget, it's the easiest and cheapest thing ever to reduce sphere pressure, volume and tighten the damping right up - or even cheaper, just move the bump stops. It often surprised novice 2cv racers how they could out-grip Caterhams through faster corners.

 

When playing around with spheres one afternoon (as one does), I tightened up a BX so it felt like a track car - it grew tricksy on the limit so transferred them onto a CX. It was just stupid, absolutely nuts, it bruised your neck.

 

Here's a 2cv with stock suspension but more power on a track - it's quite funny.

 

https://youtube.com/watch?v=hAocmae9vyE

[Talbot]

I'd like to see that video.

 

With added bonus William Woolard, which makes everything brilliant.

 

The fact that one of the CX's drives straight over a loose tyre with no effect on it's trajectory shows what hydropneumatic is for. And it's not racing. Looked bloody hillarious/ridiculous

[Guest Hooli]

That's exactly how I'd imagine narrow boat racing would look!

[forddeliveryboy]

That's a great video, Stirling Moss as cool as ever!

[Broadsword]

Having read the first post, I have to disagree at least in part. Interestingly I have both an XJ6 and a Xantia. They are both exactly as comfortable as each other in my opinion, but got there using very different methods of thinking. The Xantia runs rings around the Jag though on fast B-roads though. I'm quite sure the Xantia Activa is the record holder for the best performer on the famous Swedish car magazine "moose test", outperforming supercars.

 

Here's the thing though, whether you liked the system or loathed it, the automotive industry benefits from diversity in thinking. Homogenization as we are seeing it is not necessarily good. We all know Citroen was deliberately prevented from making the most of the technology after being merged into PSA. If two or three manufacturers had been working on the same sort of thing perhaps there would have been some very advanced setups indeed and we would be able to go around in more cars which could out-corner a fly, like the Activa. Conventional suspension with springs and dampeners only just keeps up with hydrophneumatic because it has been refined to a very high degree as a result of the entire automotive industry working on the problem of ride and handling using steel springs, shock absorbers and bits and bobs to make things not roll about. Citroen had to take on the world alone. I say they did a pretty good job and at least had the guts to try their own thing. I like people who do their own thing from time to time. It isn't necessarily subversive. It did lead to them being bought out though, Saab was a similar case. I love both.

[Tadhg Tiogar]

.... Homogenization as we are seeing it is not necessarily good. ....

In the same way that Amazon aims to monopolise everything.

[Zelandeth]

The thing about the Activa I think that surprises folks the most isn't so much what it can do and in how much comfort - but that it does it so well despite being a car from the mid 90s.

 

It's not the outright speed you can corner in it that's surprising - it's the complete poise with which it does it. The sudden left-to-right weight shift as you come off a roundabout being the best example I think...the Activa just...deals with it.

 

A lot of motoring journalists at the time criticised it for a lack of steering feel...I don't personally think that's entirely fair. It's got a very different sort of steering feel to other cars, but it's definitely there. Not something you could get used to in a few hours in a road test though.

 

I do reckon that everyone should have a shot of one though...like it or not, it's worth experiencing.

 

I count myself incredibly lucky to have stumbled unexpectedly into owning mine.

[Tadhg Tiogar]

.....I do reckon that everyone should have a shot of one though...like it or not, it's worth experiencing.

I count myself incredibly lucky to have stumbled unexpectedly into owning mine.

It took me three years to find a CX that didn't sell before I could get my hands on it.

[forddeliveryboy]

Citroen had to take on the world alone. I say they did a pretty good job and at least had the guts to try their own thing. I like people who do their own thing from time to time. It isn't necessarily subversive. It did lead to them being bought out though, Saab was a similar case. I love both.

 

Half-decent braking filtered through to most cars not long after WW2, reliably accurate steering before that, but it took some mass makers until at least the late 80s to produce cars with reliable mechanical bits, good handling and good aerodynamics.

 

Suspension is the last mechanical remnant of the horse-drawn cart and carriage. Huge energy was put into ridiculing 'unconventional' systems like the French spheres because they had a low return on investment unlike sunroofs, fancy paint and other unnecessary extras the consumer is conned into buying. Just as plenty ridiculed replacing cable-operated brakes (and probably plenty more who whined when the direct-acting brake lever on a wheel rim was 'complicated' with parts which couldn't all be fabricated in the village blacksmith's) with pistons, cylinders, valves and fluid-filled pipework, so most cannot see the point of replacing steel springing and anti-roll bits.

 

So why have so many manufacturers attempted 'improved' suspension for so long, whether Mercedes and Rolls-Royce licensing the Cit system or Audi and its magnetically-adjusted damping? Today it appears to be verging on the mainstream for much beyond the mundane, from Toyota and Mercedes to VAG, BMW and LandRover.

 

As electric vehicles become mainstream, much more will be demanded of suspension and tyres and levels of refinement will have improved beyond expectation. Previously vast spending on engine and gearbox R&D will be ending while many cars will be losing a large part of their heart, soul and identity for the more interested customer. Think BMW, for one. What will be the motor car's easiest single area for improvement? - ride, handling and comfort, I'd say.

 

When I see the complex efforts to add an air of refinement for many modern cars, whether electronically-controlled engine mounts or automatic everything, to see a crude steel bar strapped across an axle with otherwise highly-refined suspension components and bushings, I think what a strange situation, given their massively detrimental effect on how a car goes on most roads.

[Tadhg Tiogar]

.....When I see the complex efforts to add an air of refinement for most modern cars, to see a crude steel bar strapped across an axle with highly-refined suspension components and bushings, it's totally nuts given their massively detrimental effect on how a car goes on most roads.

 

It all just adds more weight.....which I think in a small way contributes to damaged road surfaces - though nothing quite as bad as extremes of weather or the incessant antics of utility contactors.

[Felly Magic]

My comment was relating to now, not the 1980s & 70s, big Citroens do not sell nowadays, not even in France, Citroen screwed themselves through heavily discounting their range constantly for years. The system has become too costly to make for the number of cars sold currently, and as all manufacturers are struggling, PSA have to cut costs wherever they can, and if it means conventional suspension, so be it