Allegro Club International

[Joe Funnell]

Hi there, I need to replace the rear nearside Hydragas unit on my 1978 Allegro but am having difficulty finding parts. I would like to know if the units fitted to Metros or MGF are the same or can be adapted to fit. I am told that the metro units have a metric thread and the Allegro units have an imperial thread for the pipe. Is there an adapter? Any info would be welcome. Thanks, Joe

[Colin T]

Hi Joe, ufortunately the Metro/MGF units will have different springing and damping rates so cannot be used on Allegros.

There were in fact 4 different types of displacers used on Allegros, I'm not sure if these can be mixed or need to be in matched pairs or can only be used strictly in a set of 4. I'm sure someone will be along to answer that soon.

The spares service have some spare displacers, there is an email address in a thread somewhere on this forum, or you can write to the address in quartic.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Richard Howe]

From previous enquiries, I believe that so long as you have the correct rate it doesn't matter if you replace them singly or as a group. Certainly people have reported replacing individual ones before.

I'm not sure if there were 4 versions though, I thought it was just 3 - S1, S2 pre-76, and S2/3 76-on. And from previous discussions, I seem to recall the spares service does have a couple but I can't remember what kinds.
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...that's why Allegro will look as good 5 years from now as it does today.

[Joe Funnell]

Hi there, Thanks both for the info. I have emailed the spares man and hope he may have the parts I need. Thanks again, Joe

[Andrew Mallett]

There are 4 different sets of numbers for hydrogas units on the parts CD.

FRONT:
31G 5311, FAM 220, FAM 2077 and FAM 4642.

REAR LH/RH:
31G 5305/6, FAM 221/2, FAM2079/8 and FAM 4641/0.

I don't know what the differences are but when each number was no longer available it said use the replacement number unit, regarding the fronts for example:

31G 5311.....NLA......Use FAM 220
FAM 220.......NLA......Use FAM 2077
FAM 2077.....NLA......Use FAM 4642

The same obviously applied to the rears as well.

If you had a car with FAM 220's on the front and you needed one replaced but only FAM 2077's were available could you replace just the one or would you have to replace both fronts and possibly both rears too with the equivalent? What were the differences in these four sets?

I seem to remember somebody saying they have coloured dots on them which signifies different rates but I am not sure, totally confused now.

Bloke from Norfolk.

[Colin T]

They do have coloured dots, a 1978 car would have the final type of displacer which has green dots.

Richard - do you mean that it is ok to replace one singularly as long as it is the same 'part number group' as the others? I agree that it isn't necessary to replace other displacers if they are the same type(part number group) and haven't failed.

I'm sure the spring/damper rates are different for the four 'part number groups', hence the different numbers as externally I think they are all the same.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Laurence]

Hi Joe,

None of the displacers you mention on the Metro/MGF (or any other) are interchangeable with Allegro units. Plus, you should renew like with like.

Is the defective displacer leaking fluid or is it just sagging on that corner? If it's sagging, maybe the plastic cup of that knuckle joint is defective. (You may have heard a squeaking/graunching sound when going over bumps etc.)

If it's sagging & that unit is very hard when 'bounced', maybe the nitrogen has leaked out of the sphere (egg).

A rivet is fitted there during manufacture which could after all these years have let the nitrogen leak out, so the suspension could sag but have no fluid leak apparent.

A way to repair this is to weld an adaptor in place of the rivet & screw a schraeder valve (tyre valve) into the adaptor, then fill with nitrogen.

High performance cars now have the tyres inflated with nitrogen, so you could probably have the displacer egg pressurised at a tyre & exhaust company. It should be inflated with a mix of 99% nitrogen 1% SF6, but I can only guess that the gas pressure should be 9.5 to 13.5 bar, if you inflate to 13.5 bar you can reduce the pressure until it feels good when you test the car.