New spheres for old!

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dnsey
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New spheres for old!

Post by dnsey »

As my Xantia 2.0 was feeling a bit firm at the rear, I decided it was time for new spheres.
Whilst thinking about purchasing a pair, I had a brainwave! Being a hoarder, I still had the pair I had removed from the front a few months ago (as well as several other old spheres). Checking the specs, I reckoned that by the time they were feeling flat, the original pressure (55 Bar) wouldn't be far off that of new rear spheres (30 Bar). OK, the damping's a bit different, but worth a try.
Half an hour with the sphere tool well spent - the rear now feels like new. Perhaps a little less damping than original spec, but certainly nothing to worry about, comfort or handling wise.
Fifty quid saved, and what would otherwise be scrap put to good use :D

Has anyone else tried this?
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AndersDK
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Post by AndersDK »

Load the trunk with luggage - or the rear seats with 2 persons.
Then enjoy the ride -
Anders (DK) - '90 BX16Image
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Mandrake
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Post by Mandrake »

Not wanting to be a wet blanket, but the damper valve characteristics between front and rear spheres are VERY different. The front spheres on a Xantia have a 1.5mm bypass hole compared to 1.1mm at the rear, this is a large difference in hole area. (The threshold valve calibrations are different too)

This is going to make the rear very soft and there will be inadequate damping. Remember too that if you significantly alter the damping / springing at only one end of the car you change the understeer/oversteer handling balance of the car.

It may be fine for casual driving, but I would have significant concerns about the safety of the handling in emergency conditions, and would not do this to my car. :?

If you had a crash that was traced to poor handling due to incorrect spheres being fitted, would your insurance pay up ? (Does incorrect spheres count as an uncertified modification to the suspension in the UK ?)

Just my 2c.

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
dnsey
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Post by dnsey »

Fair comment!

This was an experiment, and I was quite expecting unacceptable characteristics, but in practice it's only a little softer than standard - about the same difference as between standard and 'comfort' spheres, or betwen different examples of the same model with 'in tolerance' spheres, due to diffeent tyres, etc.

I would challenge anyone to be sure in a blind test whether new, correct spheres or 'reutilised' ones were fitted.

Certainly, the difference between this setup and new standard spheres is *much* less than that between new and moderately 'flat' ones.

I was aware of the difference in damper specs, and the rather greater than double hole area, but I wonder what quantitative difference it makes to compression and rebound? Unlike conventional suspension components, such data seem remarkably difficult to obtain for hydropneumatic setups.

The specs for the underinflated front spheres are, in fact, very similar to those for CX rear spheres, apart from the volume, of course. I seem to remember a discussion here some time ago about using these on Xantias, but can't remember the conclusions.

As regards insurance, I guess the greater proportion of HP cars on the road have actual sphere pressures ouside Citroen's tolerances, due to age, so would these all be considered unacceptably 'worn', I wonder? Come to that, would an insurance assessor ever test the characteristics of conventional dampers, unless they were clearly 'shot'?

Whilst I certainly wouldn't want to run a dangerous vehicle, I very much doubt that once the part number on the reused spheres has rusted over an assessor would be able to tell the difference.

I'd welcome further discussion on this, though, particularly the safety issues. Thanks for your comments so far, gentlemen.
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AndersDK
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Post by AndersDK »

In more popular terms :

I'd expect your Xantia rear end to behave like an early "D" model rear end. Not too bad, but as depicted in my previous answer, there are large riscs that rear seat passengers gets seasick.
Anders (DK) - '90 BX16Image
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