500 selected Citroën drivers
In the early 1970s, Citroën decided to recruit a group of loyal customers by using them as test drivers. The manufacturer sells them the M35, a prototype with a Wankel engine in which its own engineers have little confidence. Ultimately, Citroën buys back the models to prevent further loss of face.
Around 1970, the Wankel engine was what the electric motor with a lithium-ion battery is today: for the automotive industry the next big thing. The future. The engine was characterized, at least on paper, by greater simplicity, lower production costs and excellent running properties. Moreover, it took up very little space under the hood. Even the then arch-conservative Mercedes-Benz followed the example of the pioneers NSU and Mazda: the Stuttgart manufacturer also developed a Wankel engine.
The Wankel engine in the Citroën M35, a single-disc unit with a chamber capacity of 497.5 cc and a power of 49 hp.
Two and four cylinders Lemon old-fashioned
This optimism set Citroën’s innovation-hungry engineers in motion. They had already started developing a rotary engine in 1964, but until then this was mainly done behind closed doors. The brand’s models excelled in comfort and driving safety, but Citroën’s two- and four-cylinder engines were considered old-fashioned. The Wankel engine offered the opportunity to finally show off an innovative power source, if only because arch-rivals Peugeot and Renault did not want to know anything about the principle of the rotating piston. The Wankel engine had the potential to become another unique selling point for Citroën in France.
However, the company had learned from the teething problems of the first DSs. Before the rotary engine would find its way into a series-produced Citroën, it had to prove its reliability in extensive tests. ‘Citroën has no confidence in the Wankel engine’ was the headline above an article in the cult magazine ‘Hobby’ in February 1970, after an editor in Paris had been allowed to sit behind the wheel of an M35 for the first time. The brand had just started a rather unorthodox field test. Instead of installing the new engine in an existing model and, like the competition, settling for test bench results and test reports from professional test drivers, the French built a completely new model based on the Ami 8. It would be sold from January 1, 1970. to more than five hundred selected Citroën drivers with the aim of testing the special technology in everyday driving conditions.
Citroën M35 was not a bargain
To qualify for an M35, an interested party had to be a regular customer and drive at least 30,000 kilometers per year. Citroën committed itself to providing M35 drivers with a free replacement car in the event of breakdown or damage. The manufacturer also covered most of the repair and inspection costs. In principle, buyers only had to worry about wear parts such as tires and brake pads. Yet the 2+2-seater, which saw the light of day alongside the regular models at the Rennes factory, was anything but a bargain. With a base price of 14,000 French francs, the 4.05 meter short two-door cost about the same as a D Spécial, the basic model of the much more stately and spacious Godin, and twice as much as a Dyane.
The Citroën M35 was not overly spacious.
M35 was the only 2CV derivative with spring balls
It would be going too far to simply offer the loyal customer base a four-door Ami with a new engine under the hood. The target group had previously mainly driven the DS, so that step would be too big. To convince them, the development department equipped the cars with a modified version of the hydropneumatic suspension system. The M35 was the only 2CV derivative to feature this technology. In 1969, Citroën commissioned the coachbuilder Heuliez, based in the west of France, to provide the experimental model with a body. Heuliez was responsible for the design and production of the coupe body, but the M35 was assembled at Citroën’s factory in Rennes-La Janais.
Although the prototype looks very similar to its two-cylinder brother at first glance, they only share a few body parts. From the front, the rocker coupe, which was only available in the gray shade of Gris Nacré, is recognizable, among other things, by the special logo with the ‘double chevron’ in the rotating piston. Heuliez also did away with the chrome around the headlights and added a crease under the lights at the front. The production number of each M35 is stated on the right front fender.
To facilitate access to the second row of seats, the doors of the Ami 8 were significantly extended. The long rear side panels are taken from the Ami 8 Service, the two-door commercial vehicle version of the small station wagon. Inside, Heuliez has installed the familiar Ami dashboard in the M35, but the black upholstery of the seats – artificial leather – makes a huge difference and even evokes a bit of a lounge atmosphere in the neatly finished interior. Even in the Gran Turismo SM, which was introduced to the world a few months later, the comfortable seats would not have gone amiss thanks to their appearance. A newly designed steering wheel, clock and tachometer also took the M35 interior to a higher level.
Although Citroën charged a fairly high price for the prototypes, the project exacerbated the already tense financial situation. Because production of the M35 was partly done by hand, the Paris-based company made a loss on every example that rolled off the production line. Moreover, the first M35s delivered already provided sufficient data and information, so there was no need to build more. Citroën therefore decided to produce only 267 cars instead of the originally announced 500.
M35 specialist Aalderink keeps a register
“To cover this up, they simply skipped two hundred production numbers. After number 175 they continued with number 376,” says Sander Aalderink, founder and director of the restoration company 2CVGarage in Wormer, a town north of Amsterdam. He is probably the most famous M35 specialist and an impressive number of prototypes have passed through his hands. On his website mengm35.com he keeps a register of ‘survivors’ and there he explains the history of the M35. He also has spare parts made.
Citroën’s Wankel engine also needed a drink of oil. That is why the advice was to check the oil every 250 kilometers.
Bought back M35s but waived warranty if retained
After stopping the practical test, Citroën offered to buy the cars back from the owners. Most customers accepted the offer, but there were also people who wanted to keep their car. Citroën accepted this on one condition: the owners had to sign a declaration that they waived the supply of spare parts and any warranty.
Technical data Citroën M35
Single-disc Wankel engine (type Comotor KKM 613), longitudinally placed at the front, register carburetor (Solex 18/32 HHD)
Chamber capacity 497.5 cc
Compression ratio 9.0:1
Max. power 36 kW/49 hp at 5,500 rpm
Max. torque 70 Nm at 2,745 rpm
Drive front wheels via manual four-speed gearbox
Dimensions (l/w/h) 4.05/1.56/1.35 m
Wheelbase 2.40 m
Weight 815 kg
Tire size Michelin
Top speed 144 km/h
0-100 km/h 19.0 s
Consumption avg. approx. 10 l/100 km (1:10)
Starting price (1970) 14,000 French francs
The Netherlands has a lot of knowledge of the Citroën M35. You can find one at Sander Aalderink’s 2CV garage in Wormerveer, but also at Visscher Classique in Buren.
This is a shortened version of an article that previously appeared in AutoWeek Classics 13 2022.
– Thanks for information from Autoweek.nl