If the spheres were new or reconditioned make sure the ride height is set correctly, also you should check the rear height lever is not broken or the clamp loose. The plastic coupler £3 at citroen very often comes off or breaks.
Hope this helps, Jim.
Cheese., August 2011
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I can answer this question...
My Xantia 1998 1.9 has new sphears fitted but the suspension is hard ?