Renault R40

One of these was directed to the improvement of the horizontal rubber spring suspension system that, apart from being less reliable than originally hoped for, caused an uncomfortable ride, high track and tread wear and an unfavourable weight distribution.

[1] However, after tests from 19 May until 26 December 1938, an AMX design using six vertical coil springs covered with 8 mm armour plating with twelve road wheels per side, was selected on 16 February 1939.

Also, the longer track links caused a heavy clattering during road travel, reminiscent of the noise made by the Renault FT. Fuel consumption was 40% higher.

In late 1939, retrofitting the existing vehicles with the cheaper Renault vertical coil suspension was considered, as it could be done by field workshops and thus pose less of a burden to French industry.

It coincided with a number of other improvements, such as a longer and thus much more powerful SA38 Long 35 37 mm gun in the adapted cast APX-R1 turret, giving the type a good antitank capacity, and a tail to facilitate climbing.

In May 1940, the R 35 had the largest production of any Allied (or indeed Western) tank but it was planned to having it surpassed by that of the much faster "H 39", reflecting the emphasis on the formation of new armoured divisions, for which the slow R 40 was less than ideal; the "new" suspension was really rather old-fashioned and could not be combined with a high speed, as earlier experience with the Char D3 and Renault VO projects had shown.

Nevertheless, apart from donations to allies and units already formed in June, another 800 vehicles were needed to replace the Renault FTs of eight existing battalions and raise eight new battalions to bring their number to the planned final total of fifty light tank BCCs (Bataillions de Chars de Combat), forty of these equipped with Renault tanks.