Editing Citroën 2CV (section)

=== Suspension ===

The suspension of the 2CV was very soft; a person could easily rock the car side to side dramatically. The [[swingarm|swinging arm]], fore-aft linked<ref>{{cite thesis |url=https://www.researchgate.net/publication/290866140 |title=An Investigation into the Dynamics of Vehicles With Hydraulically Interconnected Suspensions |last=Smith |first=Wade |publisher=University of New South Wales |location=Australia |at=Figure 2 Schematic of the early Citroen 2CV suspension |date=2009-06-01 |doi=10.13140/RG.2.1.1702.5048}}</ref><ref name="j.ymssp.2022.108998">{{cite journal |last1=Zou |first1=Junyi |last2=Guo |first2=Sijing |last3=Guo |first3=Xuexun |last4=Xu |first4=Lin |last5=Wu |first5=Yongjia |last6=Pan |first6=Yu |title=Hydraulic integrated interconnected regenerative suspension: Modeling and mode-decoupling analysis |journal=Mechanical Systems and Signal Processing |date=June 2022 |volume=172 |pages=108998 |doi=10.1016/j.ymssp.2022.108998 |url=https://www.researchgate.net/publication/359105946 |access-date=20 July 2023}}</ref><ref name="citroenet/2cv/1949">{{cite web |title=Citroën 2CV 1949 |url=https://www.citroenet.org.uk/passenger-cars/michelin/2cv/history/1949.html |website=citroenet.org.uk |access-date=20 July 2023}}</ref> suspension system with inboard front brakes had a much smaller [[unsprung mass]] than existing [[coil spring]] or [[leaf spring]] designs. The design was modified by Marcel Chinon.{{sfnp|Reynolds|2005|p=34}}

The system comprises two suspension cylinders mounted horizontally on each side of the platform chassis.<ref name="j.ymssp.2022.108998"/><ref name="Julian-Edgar/2CV-suspension">{{cite book |last1=Edgar |first1=Julian |title=Car Suspension: - Over 120 Years of Ride and Handling |date=20 August 2021 |publisher=Amazon Digital Services LLC - KDP Print US |isbn=979-8-5329-4523-4 |language=en}}</ref><ref>{{cite web |last1=Edgar |first1=Julian |title=Citroen 2CV suspension |url=https://www.youtube.com/watch?v=j7pFxgDmZXQ |website=youtube |access-date=20 July 2023 |language=en |date=August 31, 2021}}</ref> Inside the cylinders are two springs, one for each wheel, mounted at each end of the cylinder.<ref name="citroenet/abandoned">{{cite web |title=Front to rear interconnected suspension - Abandoned technologies |url=https://www.citroenet.org.uk/miscellaneous/abandoned/abandoned.html |website=citroenet.org.uk |access-date=20 July 2023}}</ref> The springs are connected to the front leading swinging arm and rear trailing swinging arm, that act like [[bellcrank]]s by pull rods (tie rods).<ref name="silodrome/2cv-history">{{cite web |title=A Brief History of the Citroën 2CV |url=https://silodrome.com/citroen-2cv-history/ |website=Silodrome |access-date=20 July 2023 |date=26 November 2019}}</ref> These are connected to spring seating cups in the middle of the cylinder, each spring being compressed independently, against the ends of the cylinder.{{sfnp|Reynolds|2005|p=34}}<ref name=Marsh1>{{cite web|first=Julian |last=Marsh |url=http://www.citroenet.org.uk/passenger-cars/michelin/2cv/cutaway/cutaways.html |title=Citroën 2 CV cutaway images |publisher=Citroenet.org.uk |date=10 June 2000 |access-date=17 April 2014}}</ref><ref name="autospeed1">{{cite news |url=http://www.autospeed.com/cms/gallery/article.html?slideshow=0&a=111302&i=8 |title=2CV suspension design |publisher=Citroën |via=Autospeed |access-date=19 January 2019 |archive-date=4 November 2016 |archive-url=https://web.archive.org/web/20161104034142/http://www.autospeed.com/cms/gallery/article.html?slideshow=0&a=111302&i=8 |url-status=dead }}</ref><ref>{{cite web |url=http://www.autospeed.com/cms/gallery/article.html?slideshow=0&a=111302&i=8 |title=Images for article 'Five Ideas Worth Revisiting' |access-date=19 May 2012 |archive-date=29 March 2012 |archive-url=https://web.archive.org/web/20120329033731/http://www.autospeed.com/cms/gallery/article.html?slideshow=0&a=111302&i=8 |url-status=dead }}</ref> Each cylinder is mounted using an additional set of springs, originally made from steel, called "volute" springs, on later models made from rubber. These allow the front and rear suspension to interconnect.{{sfnp|Reynolds|2005|p=33}} When the front wheel is deflected up over a bump, the front pull rod compresses the front spring inside the cylinder, against the front of the cylinder. This also compresses the front [[volute spring]] pulling the whole cylinder forwards. That action pulls the rear wheel down on the same side via the rear spring assembly and pull rod. When the rear wheel meets that bump a moment later, it does the same in reverse, keeping the car level front to rear. When both springs are compressed on one side when travelling around a bend, or front and rear wheels hit bumps simultaneously, the equal and opposite forces applied to the front and rear spring assemblies reduce the interconnection.<ref name="TheTin" />{{unreliable source?|date=October 2016}} It reduces pitching, which is a particular problem of soft car suspension.<ref name="TheTin" />{{unreliable source?|date=October 2016}}

The swinging arms are mounted with large bearings to "cross tubes" that run side to side across the chassis; combined with the effects of all-independent soft springing and excellent damping, keeps the road wheels in contact with the road surface and parallel to each other across the axles at high angles of body roll. A larger than conventional steering [[castor angle]], ensures that the front wheels are closer to vertical than the rears, when cornering hard with a lot of body roll. The soft springing, long suspension travel and the use of leading and trailing arms means that as the body rolls during cornering the wheelbase on the outside of the corner increases while the wheelbase on the inside of the corner decreases. As the cornering forces put more of the car's weight on the outside pair of wheels the wheelbase extends in proportion, keeping the car's weight balance and centre of grip constant, promoting excellent road holding. The other key factor in the quality of its road holding is the very low and forward centre of gravity, provided by the position of the engine and transmission.{{sfnp|Reynolds|2005|p=21}}

The suspension also automatically accommodates differing payloads in the car- with four people and cargo on board the [[wheelbase]] increases by around 4&nbsp;cm (2&nbsp;in) as the suspension deflects, and the [[castor angle]] of the front wheels increases by as much as 8 degrees thus ensuring that ride quality, handling and road holding are almost unaffected by the additional weight.{{sfnp|Reynolds|2005|p=38}} On early cars friction dampers (like a dry version of a multi-plate clutch design) were fitted at the mountings of the front and rear swinging arms to the cross-tubes. Because the rear brakes were outboard, they had extra tuned mass dampers to damp wheel bounce from the extra unsprung mass. Later models had [[tuned mass damper]]s ("batteurs") at the front (because the leading arm had more inertia and "bump/thump" than the trailing arm), with hydraulic telescopic dampers / shock absorbers front and rear. The uprated hydraulic damping obviated the need for the rear inertia dampers.{{sfnp|Reynolds|2005|p=58}} It was designed to be a comfortable ride by matching the frequencies encountered in human bipedal motion.{{sfnp|Reynolds|2005|p=32}}

This suspension design ensured the road wheels followed ground contours underneath them closely, while insulating the vehicle from shocks, enabling the 2CV to be driven over a ploughed field without breaking any eggs, as its design brief required. More importantly it could comfortably and safely drive at reasonable speed, along the ill-maintained and war-damaged post-war French Routes Nationales. It was commonly driven "Pied au Plancher"—"foot to the floor" by their peasant owners.<ref name="TheTin" /><ref>{{cite journal|title=The 2 c.v. 375c.c. Citroen—Unorthodox Suspension|journal=[[The Motor]] |date= 27 September 1950}}</ref>