Note No. 868 (7 April 1970): the maintenance cost of hydropneumatic suspension quantified

In this document

This internal note from the Citroën After-Sales Service, signed by H. Vigneau and addressed to Mr. Ravenel, responds to a request from 17 March p. 125 regarding the maintenance cost of hydropneumatic suspension.

The method: two cross-referenced surveys

A first survey conducted in 1969 covers IDs from 1967-1968 equipped with LHM (mineral hydraulic fluid): it calculates the oil change (every 30,000 km) at 0.002 F/Km and hydraulic repairs at 0.001 F/Km, i.e., 0.003 F/Km, or 180 F for 3 years and 60,000 km p. 125.

A second method, based on the cumulative sales of spare parts in 1969 (cylinders, spheres, ball joints, suspension arms, pumps...), results in 0.004 F/Km — parts and labour included p. 126. The note concludes with a range of 0.003 to 0.004 F/Km, i.e., "from 180 Fr to 240 Fr for 3 years and 57,000 Km" p. 126.

Comparison with conventional suspensions

In the absence of reliable data, the department estimates the lifespan of shock absorbers between 10,000 km (204 in hilly regions) and more than 40,000 km (R16 in hilly regions), adopting an average "closer to 40,000 Km than 20,000 Km" p. 126.

Over 40,000 km, shock absorbers cost 0.009 F/Km for the R16 and 0.014 F/Km for the 204 p. 126. The 504 data remain incomplete ("?").

The note concludes: "Hydraulic suspension costs significantly less in maintenance-repair than a conventional suspension", specifying that "more than half of its cost comes from the fluid" p. 126.

Context

At that time, hydropneumatics had equipped the DS and ID since 1955, and Citroën sought to demonstrate the economic reliability of this technology against conventional suspensions such as those of the Renault 16, the Peugeot 204 and the 504, then direct competitors on the French market. The acronym LHM designates the mineral hydraulic fluid introduced gradually during this period to improve the system's durability over time.

Archivist's perspective

This document is valuable because it provides a quantified argument, rare in this collection, likely intended to respond to recurring criticisms regarding the perceived maintenance cost of Citroën hydraulics. It seems to be part of ongoing work by the After-Sales Service to objectify the system's performance against the competition, in line with reliability surveys conducted from the early 1960s, such as the one on hydraulic leaks of the DS 19. The numerous highlights and the handwritten brace surrounding the conclusion p. 126 suggest that this finding, favourable to hydropneumatics, was particularly highlighted by its recipients.