Citroën–Michelin correspondence on rubber suspensions (May 1948)

In this document

This file gathers three letters exchanged in May 1948 between the Citroën factory (Mr Cadiou, Design Department) and the Michelin factory in Clermont-Ferrand (Messrs Chataigner and Saint-Frison), concerning two related technical subjects.

Letter of 11 May 1948: the T.P.V. suspension

Michelin informs Citroën that Mr Boulanger has compared steel spring suspensions and rubber spring suspensions, concluding that the "former are superior to the latter" p. 59. Michelin requests to meet "the person in charge of suspension design" to seek the reasons for this inferiority p. 59. A handwritten note in the margin indicates a stamp "14 MAY 1948" followed by the signature "M. Magès" p. 59.

Letter of 4 May 1948: the "suspension bibax"

Michelin mentions the examination of an industrial production of more than 1,000 "bibax" per day and requests the corresponding assembly and detail drawings p. 60. A handwritten annotation "Mags." appears at the bottom of the page p. 60.

Response of 24 May 1948 (Michelin to Citroën)

Michelin replies to the letter of 11 May: "Mr MAGES is in charge of rubber suspensions" p. 61. The letter specifies that there is no evidence to suggest that the inferiority noted by Mr Boulanger stems from the rubber material itself, as "other factors" are at play p. 61. Tests are underway, and Mr Magès is to travel to Clermont-Ferrand to inform Mr Chataigner p. 61. In a postscript, J. Cadiou indicates that it is not possible to respond to the request for mass-production bibax plans at this time p. 61.

Context

Michelin, majority shareholder of Citroën since the 1930s, collaborated closely with the manufacturer on materials and suspension technologies — a field of intense experimentation in the late 1940s, ahead of the development of the future DS and its hydropneumatic suspension.

The acronym T.P.V. (Toute Petite Voiture) refers to the project that would become the 2 CV: Paul Magès was already conducting the first hydropneumatic suspension tests for it in May-July 1946 (Notebook of the first 2 CV hydropneumatic suspension tests (May-July 1946)), which places the exchange on rubber suspensions mentioned here in the continuity of these T.P.V. researches, even if the document itself does not explicitly state it beyond the title "T.P.V. SUSPENSION".

Archivist's view

This exchange is valuable because it documents, at a precise date (May 1948), the moment when Paul Magès is explicitly designated as the person responsible for rubber suspensions at Citroën — an official attribution from Michelin itself p. 61.

It also shows that Magès was then working in parallel on several suspension paths (steel, rubber, and the mysterious "bibax"), in a period when the company was still looking for the best technical solution — before the hydropneumatic path, already explored by Magès a few years earlier, prevailed. This file can be compared to the differential interaction hydropneumatic suspension plans of 1944, which testify to earlier research conducted by Magès on a principle finally adopted for the DS.

The tone of the letters, factual and administrative, suggests the tensions between the two companies regarding the choice of technical solutions and the sharing of industrial information (the "bibax" plans were not transmitted).