"If you've had the rear suspension of your Saxo lowered by adjusting the torsion bars, this annoying 'ping' noise appears to be fairly common. This can also occur however on Saxo's running with un-modified suspension.
The 'ping' noise seems to be more noticable in wet weather... luckily, there is a very simple solution to this problem... usually!
At each side of the rear axle, the anti roll bar has an end plate, which is bolted in position with a 13mm bolt. The most common cause of the 'ping' noise is due to this 13mm bolt working loose.
When loose, the anti roll bar end plate is able to rotate slightly as pressure is transmitted to the anti roll bar, through the rear suspension... creating a high pitched 'ping' noise!
The solution...
To get rid of this annoying noise you need to jack up the rear of your Saxo and remove the rear wheels. Working on one side of the car at a time, remove the 13mm retaining bolt, which secures the anti roll bar end plate in position.
Apply a thin layer of grease (preferably copper grease) to the threads of the bolt and wind it back into position. Ensure the bolt is tensioned well, but dont overtighten it, as the threads can easily be damaged!
By lubricating the bolt and re-tightening it in position properly, the 'ping' noise should disappear... You may only need to do this to one side of the car, but it is good practice to check both sides, whilst you are underneath the car!
And that's hopefully all there is to it... the 'ping' noise should be gone.
I hope this information is of some use to you..."
Taken from FAQ
