Hydrolastic Colour Coding

[mk1]

What is the colour coding across the range of hydro displacers?

I know Red & Silver, but other than that they are a bit of a mystery to me.

[12g295]

Early cars pre 68

Normal front – no marking part no 21A 1477
rear - no marking part no 21A 1703

Stiff front and rear 1 Yellow band part no C-21A 1705

Hard front 1 Red band part no C-21A 1819
Hard rear 2 Red bands part no C21A 1821

Late cars post 68

Normal front and rear 1 orange or green band part no 21A 1804

Stiff front and rear 2 orange bands part no 21A 1811

Hard front 1 Blue or silver band part no 21A 1872
Hard rear 2 Blue or silver bands part no 21A 1874

[mk1]

Thanks very much.

[Austin Cooper]

Someone on the MCR has made a really decent list of them. There is a link to it in the 9th post of this topic http://forum.minicooper.org/showthread.php?t=9464

[Mini4Ever]

That very same list is even in Mark's main pages: https://mk1-performance-conversions.co. ... _units.pdf

[mk1]

Ha, ha, even I can't be expected to remember everything that's on the MK1 site. It currently runs to just over 1.3Gb

[LMM76C]

The "Blue" units seem to have been available as early as late 1966? I know of a private 998 Cooper used on the 66 RAC that went to Abingdon to have comp units fitted and blue was the colour mentioned. By January 1969, when i bought them (and probably much earlier in 1968), silver was available across the counter at BL dealers as the hard competition units. Prior to the 66 Monte, the Gp1 works cars were being prepared with red competition units, according to Stuart Turner.
Certainly the matches std/comp were
Unmarked or yellow/red
orange/blue
green/silver

[Ronnie]

I think that the red (competition) units were the same rating as the silver (std S) displacer, but they had a .150" or .180" spacer built in to raise the suspension.

[Will Grant]

I think blue units came in from midish (6/7?) 66.

[formulaphoto]

Early cars pre 68

Normal front – no marking part no 21A 1477
rear - no marking part no 21A 1703

Er.... are rear displacers physically different from front displacers? I think I've just put four units of the same part no back into my subframes!

W

[66S]

Hi Warwick,
As far as I know, the only external difference is the distance at the hose end from the top ledge down to the diaphragm. Cooper S displacers are 5/8" to 3/4" and regulars are 7/8" to 15/16". This seems to because there is extra rubber (strength) in the Cooper S ones, meaning firmer action.
Some numbers were used front and rear, some had different displacer numbers front to rear.

Regards
Al

[wanganui1071]

Hi All
Re identifying displacer units .
Is the part no moulded into the rubber as per the standard units .ie 21A 1477
And then identified by colour bands , or a stamped or moulded no.
I have a set of green banded rear s displacers, i know they were removed from a 1966 English s but they are rubber moulded no 21A1477
Just trying to clarify .
Many thanks

[richardACS]

Interesting question.

Where are the part no's shown?

What happens to the handling if the front and rears are mixed up?

I've never noticed then being sold as front or rears

[Peter Laidler]

So far as I could ever make out, the number cast into the top rubber moulding, 21A1477 ISN'T the part number of the unit. It is the Dunlop/Moulton casting number of the rubber within the top part of the hydro unit. This top part is standard across the range.

This top rubber moulding, moulded into the upper 'cup' part is the 'lastic' part of hydroLASTIC. It gives the resilience you need in the hydrolastic system due to the fact that you can't compress a liquid.

What makes the units supposedly different is the (probably by now) extinct internal valving.

What happens if you mix the fronts and rears? Nothing....., they were all the same towards the end of production. So one must ask the question that if they were all interchangeable F to R later, why weren't they the same before.

As for the different stifnesses, all I would ask is this. Has anyone ever seen any reference to ascertain exactly how the stiffness was quantiified by, say, fluid flow or a measure of resistance? Nope, me neither

As I always say, I'm always open to be shot down but hydro has always needed some hard, open and frank talk

[Hipwell]

Part number is stamped on the unit, along with a date code. Impossible to see on rusted units.

Given how rusty the internals get, I doubt the damping on them is going to vary a huge amount across the different units.
Although as noted some of the piston 'cups' are longer.

[mab01uk]

Extra info for reference....




Section through a Mini Hydrolatic Unit - (Sectioning & Photo: Tim of Minimail)



Lots more technical info and background on Hydrolastic units are in this thread linked below.
The future of Hydrolastic suspension:-
viewtopic.php?t=14542

[richardACS]

Thanks to you all for the added information.

It makes one wonder if they're still upto purpose, I will take a close look for the part number and date. My car came with a set of four with two orange slashes. They bench tested with no leaks and still original hoses then caused a problem of my own making (i.e. lifting the subframe up and down to see if it had properly located) and in the process forgot about the hydro pipes which had snagged and then stretched - cue leak.

Very stupid of me because the hoses and fittings were in nice condition (from New Zealand/no salt).

I had a further set that came from the USA and fitted those to the front but one has started weeping.

I did however manage to purchase from Fred Walters a couple of sets of original hoses that had new ends crimped on (very neat job) and so will set about fitting these to the original pair that I damaged and hopefully then have a matching 'two slash orange' set that don't leak/weep...

[rogerotto66s]

I came across this some ago when I was researching my 1966 “S”
Source unknown.

IMG_4322.png

[Spider]

They weren't all painted either and often the part number is quite difficult to find and read.

[abs]

The colour coding is only any use if it`s on a pair of old stock completely unused units otherwise the valving has rotted away hence the need for shock absorbers.