My son's 2006 e91 330d SE touring corners well and rides smoothly.
However, undulations cause the car to pitch and wallow at the back. The car rides over crests as expected, but then seems to bottom out very quickly accompanied by a loud 'thunk' if severe enough.
This can be bad when driving alone and pretty horrendous with a full load;hanging bikes off the towbar - vv bad news!!!
My gut feeling is, the dampers work ok, but the car has been fitted with overly soft springs or have deteriorated.
Also the rear tyres seem to wear the inside edge prematurely,i've been told this is normal,although my own e92 coupe tyre wear is fine.Both cars run bmw approved runflat tyres and we check pressures regularly.
grateful for any feedback,or anyone who has 'sensibly 'uprated their e9x
suspension,as he lives in the north of scotland lowering is not an option.