Report on TPV suspension comparative tests — 4 and 8 May 1948

In this document

This report documents two days of comparative suspension tests on the T.P.V. vehicle ("Toute Petite Voiture", ancestor of the future 2CV), conducted in early May 1948.

Tests of Tuesday 4 May

Four cars are compared, all in 375 cc p. 63:

• A.6: series suspension
• A.11 bis: rubber suspension with interaction
• B.9: rubber suspension without interaction
• L: single spring interaction

The tests take place on the Marchainville road, in the presence of Messrs. Lefebvre, Lavoix, Magès, Cadiou p. 63.

With 2 people (50 kg), the ranking is A.11 bis - A6 - L - B9, with car L appearing "dry" and B9 having "galloping" p. 63. With 4 people (60 kg in the rear seats), the ranking is partially reversed: B9 - A6 - L - A.11 bis, although with a "somewhat large pumping amplitude" for the A6 at the rear p. 63.

Tests of Saturday 8 May

Same cars, now equipped with 125½ HSP tires, tested along the property wall with the addition of Mr. Boulanger p. 63-64. With 2 people, the A6 is judged "the best", L "good, acceptable", while A.11 bis and B9 (rubber susp.) are "less fluid" and transmit road shocks p. 63. With 4 people, the A6 remains good despite exaggerated rear pumping, with car L being "drier" at the front and rear p. 64.

Conclusions

The report concludes on the continuation of the A.6 series suspension for vehicle A, with a path for improvement towards the L solution (cheaper, simpler), to be tested with a galloping reaction lever created by Mr. Lavoix before 30 May p. 64. The improvement of the rubber/rubber suspension is abandoned, while noting that its perceived stiffness on small oscillations remains to be understood p. 64.

Context

The TPV designates, in Citroën history, the program that would lead to the 2CV, presented in 1948. These comparative tests illustrate the technical trial and error preceding the final development of the interaction suspension, with several competing solutions (springs, rubber) still being evaluated at this pivotal date.

Archivist's perspective

This document offers a rare snapshot of the experimental work of Paul Magès and his team (Lefebvre, Lavoix, Cadiou, Boulanger) in the field, at a time when the rubber interaction suspension — although explored for several years in the file, see the plans for hydropneumatic suspension with differential interaction — is finally discarded for vehicle A.

It seems that this finding of failure directed research towards other solutions, probably in the continuity of the test program mentioned in the BEA 1945 work programs.