Originally Posted by jdd

It’s worth checking the 4 sway-bar mount bolts, and while you’re at it check the remaining bolts that also mount the under-tray.
If the sway-bar mounts are loose and have been loose for a while you may need to replace the bushes.
I also had a similar clunking problem and replaced the sway bar links to discover it didn’t totally fix the problem.
After some further investigation I discovered a couple of the bolts that mount the sway-bar were loose along with a couple of the under-tray bolts. A friends X5 also had exactly the same problem recently. In both cases we didn’t need to replace the sway-bar mount bushes and tightening to bolts was sufficient to stop the clunking.