Time for a suspension of disbelief.
Hydropneumatic. Whenever this word is mentioned among those with even a fleeting interest in cars, the word Citroën usually follows. And with good reason; this much praised suspension system was an indispensable factor in cementing the double chevron’s reputation for ride comfort and Avant Garde engineering.
It is a little known fact however that competitor Peugeot (in those days known, in contrast to Citroën, for conventional and proven engineering) would nearly introduce its own version of hydropneumatic suspension in the 404.
Starting in 1953, Sochaux engineers worked on a hydropneumatic suspension system which was installed in a few secret 403 prototypes. In 1957 Peugeot management, doubtless spurred on by the spectacular introduction and resultant publicity storm around Citroën’s DS 19, decided that the new suspension would be made available as an option for the upcoming 404 model, under the name Oléopneumatique.
The Peugeot system differed from Citroën’s in that it was a closed circuit system with a continuous pump as opposed to an open system. Two versions were planned: one for use only on the rear axle, and one for all four wheels.
The idea behind this was to offer buyers a range of suspension methods when choosing a 404 while also allowing the more traditionally inclined Peugeot customers to stick to the tried and tested coil springs if they chose.
As did Citroën before, Peugeot encountered numerous reliability issues with the new-fangled technology. Still, Sochaux was confident that these teething problems would be eliminated by the time the Oléopneumatique was to be installed in production cars.
The 404 Oléopneumatique on the testbed.
The 404 was introduced in 1960, with the Oléopneumatique option planned to be presented for the 1962 or 1963 model year. However, in late 1960 Peugeot CEO Maurice Jordan ordered the suspension (no pun intended) of the project, even though nearly 200 million Francs had already been invested and several pre-production vehicles were already undergoing real world testing.
Why? Naturally precautions had been taken to ensure that the Peugeot system would not violate Citroën’s intellectual property, but even so, Jordan was wary of legal trouble with the double chevron and the unwanted publicity that might come with it. On top of that, marketing-wise there was every reason to expect Citroën to portray the Oléopneumatique as a copy of their work even if it did not actually infringe on its patents.
The most salient reason however is of a more strategic kind. With the common market to become a reality a few years later – 1968 – Peugeot was seeking an alliance with Citroën, the latter being in the stronger negotiating position at the time (some years later it would be the other way round).
Negotiations took place, and one of the concessions Peugeot was forced to make was abandoning the Oléopneumatique- in vain as it would turn out because the alliance would come to nothing.
In 1966 François Gautier succeeded Maurice Jordan as CEO, declared no further interest in the Oléopneumatique and cancelled all further development – and that meant the end of the road for Peugeot’s attempts at challenging Citroën’s famous Hydropneumatique.
Driven To Write 
Excellent article, Bruno. I never knew this. Years later Peugeot did use a Citroën based system on rear suspension of the 405 Mi16
Yes, interesting stuff, thank you Bruno.
The 404 / DS mash-up is bonkers, of course, but the high-level indicators integrate rather well, don’t you think?
Not mentioned is the fact were also plans for the 404 Oléopneumatique to feature a V8 engine to further one-up the DS, however it is not clarified whether the engine was derived from the Peugeot 404 XC* 4-cylinder (akin to how the Renault A-Type was derived from an inline-6 in Project 114) or less likely a clean-sheet design.
Though if Peugeot was indeed looking at a V8 for the 404, one would assume it would have been a pretty small capacity V8 engine to fit into French tax regulations without creating a huge gap in the range like Citroen did between the 2CV (and derivatives) and the DS.
* – Out of interest, would it be accurate to say the Peugeot XC engine in the 404 would evolve into the XM and XN engines used in the 504 and 505?
What an interesting background story, Bruno, thank you.
Though I wince once more at the shedding of 200 million francs to effectively save face. But if you consider the legal costs, the re-engineering, the pay-offs of the big cheeses due to the restructuring…a drop in the ocean., I suppose.
Wow – very interesting, and a completely new story to me – thank you.
By weird coincidence, HubNut, the classic car channel, did a review of the 404, recently.
It appears that although it was more conservatively engineered compared with the Citroën DS / ID, it was still well-engineered and more advanced than BMC’s equivalents. On the other hand, although it was a long-lived commercial success, it’s still mind-blowing that this was launched well after the DS & ID (no disrespect to Peugeot).
Fascinating article, the exact sort of article that makes this site so interesting!
Thank you all for your kind comments. And Daniel: yes, I surprised too that those ID/DS “trumpets” are an almost natural fit on the 404’s C-pillars. The taillights (which I think are Fiat 2100/2300 items) not so much because on the Fiat the ends of the rear wings\y are canted as opposed to the 404’s perfectly vertical ones.
Rover was also developing pressurised anti-roll and self-levelling suspension in the 1960’s – see below. Seeing a P6/P7 rise-up Citroen-like is strangely satisfying:
Wow, I can’t believe I missed this fascinating video earlier: Thank you for posting it!