When I removed the
displacers from my Sept 1970 Cooper S I noticed they were different to a set of Mini K
displacers of roughly the same age in one obvious externally visible aspect. The moulded rubber component inside the metal cylinder of the S displacer was closer to the top rim than the non-S Mini K displacer. I figured this might be the method of creating a stiffer spring setting and hence a simple way to easily identify a Cooper S (and Clubman GT) displacer from a non-S displacer. Several people with much greater knowledge of hydro suspension than me agreed with my suggestion, however there's another view that all early
displacers (until around March/April 1968) regardless of application (S or non-S) have the higher rubber fill and after that all
displacers, regardless of application, have the lower fill.
Here's a photo that compares one of my S
displacers on the left with a MIni K displacer on the right. You can see the difference in height of the rubber surface.
Attachment:
Front Displacers.jpg
The displacer from my car has the part number 21A2014 and date 69 embossed in the steel case.
Attachment:
Displacer 21A2014 69.jpg
This lines up with the part numbers listed in a table in the BMC Australia displacer engineering drawing (YDO6 is Cooper S and YDO5 other Mini models).
Attachment:
AYA4090 Spring Unit Specs wm.jpg
In an effort to get an agreed position on this I'm asking for any displacer photos to be posted here that clearly show the embossed part number, date and moulded rubber level.
By the way, ignore the part number 21A1477 that appears on the surface of the rubber in the bowl. It's a common number used across all
displacers.