The "frotteurs" prevent the wheel to "follow" the frequency of the induced force. The "batteur" is positioned directly above the vibrating plate and is capable to follow. The hydrolic shocks are "to far away" from the vertical induced forces and undergo only a small fraction of the 6 mm move from the plates. The shocks cannot follow the movement correctly and sometimes even work against the vibrations. They hardly can come "in fase" with the induced forces. Sorry, for this explanation to tell that the test is wrong for our Citroen suspension.

The (UK) MOT tester's manual has a section devoted to the peculiarities of the 2CV/Dyane/Ami and what to expect. That doesn't mean today's MOT testers know the section exists and refer to the guidelines within. Owners should be made more aware of the existence of the guidance and bring it to the attention of their MOT tester before he/she starts the test.

@Jonathan; is there any possibility to get a copy of the MOT pages about the testing of the A-types suspension ?

"modern" mecanics don't understand old cars. The local citroen dealer did refuse to help a man with his Dyane because the car didn't have a computer plug.

I don't have access to the relevant documentation, sorry. A good friend and fellow 2CV'er is an MOT tester and brought my attention to the fact.

So if your good friend is a MOT tester he must have the papers. Can you ask him to copy the section relevant to suspension testing ?

The MOT Testers manual is available on line if you want to look yourself.

https://www.gov.uk/guidance/mot-inspect ... l-vehicles

John

Many thanks !!!