Hydraulic suspension tests from 18 May 1949 at Petit Clamart

In this document

Context of the test

The document is a report on road tests of the Citroën hydraulic suspension, carried out on 18 May 1949 on the Paris - Les Bruyères - Petit Clamart circuit p. 76. The tests brought together Messrs. Boulanger, Cadiou, Duclos, Lefebvre and Magès p. 76.

The protocol specifies that inflation and damping remain identical to the previous "B - C - D" tests (1.3 and 1.6 tyres); the only variable tested: the roll stiffness p. 76.

The settings tested

Five settings are compared, designated by letters and defined by the position of the front setting (hole number) and the rear diameter (Ø):

Observations of the test drivers

For setting E, Mr. Boulanger notes a "smoother" ride, "forgetting small shocks", slower but larger amplitude transverse movements, and "heavy steering"; Mr. Duclos mentions an "impression of not holding, but holds very well" p. 76.

Setting F is judged to have "very acceptable fluidity" by Boulanger, who prefers it on this point, while Messrs. Lefebvre and Magès note having "lost road holding" p. 76.

Setting G arouses Boulanger's enthusiasm: "remarkable stability", "extremely pleasant", more stable than the previous settings, with "zero pumping and pitching" but amplified lateral shocks; he describes this setting as "Citroën Quality" p. 76-77.

Setting H is described as having "smoother lateral jolts" but lateral shocks not as good as setting A (mentioned as a reference); Duclos confirms "less frequent" lateral shocks and impeccable road holding p. 77.

Setting I is classified "among the bad settings from the point of view of lateral shocks", without regaining the pleasant sensation of setting G, "but not bad all the same" p. 77.

Handwritten dates "18.5.49" appear at the top and bottom of page 76, as well as a vertical annotation mentioning "Mr. Magès" (uncertain reading) p. 76.

Context

These tests are part of the long development phase of the hydropneumatic suspension, a revolutionary system developed by Citroën and of which Paul Magès is one of the inventors. Pierre Boulanger, then president of Citroën, was personally involved in these road tests, which testifies to the strategic importance of the project.

This work would prepare for the arrival of the front-wheel drive equipped with this suspension, then, a few years later, that of the DS presented in 1955.

Archivist's perspective

This document concretely illustrates the empirical and iterative method used by the Magès team: multiplying settings, collecting the subjective impressions of several drivers while fresh, and comparing the compromises between stability, comfort and road holding.

The mention of the "Citroën Quality" setting p. 77 seems to indicate that a perceptible comfort standard was already being sought at this date, well before the commercialisation of the DS.

This report is probably part of a series of comparable tests; it could be usefully compared with the Folder "Theoretical study – hydropneumatic suspension 1943/44" and the Hydropneumatic suspension plans with differential interaction and automatic levelling, which document the more theoretical phases of the same research.