[Angel67]

I have done some more work on this.

The clearance between the heads of the screws in the strut mount and the top of the aluminum top hats is 7mm without the washers. Add another 5 mm or so for the washers, makes 12 mm of clearance, without any load. The strut mounts have a rubber bushing that is bonded to and holds the metal cylinder through which the shaft of the strut passes and onto which a bolt is fastened at the top to hold the shaft. The top edge of the cylinder is about 9 mm below the top edge of the strut mount, without any load.

Under load (static load), in my car, the top edge of the cylinder is level with the top edge of the strut mount - so the bushing has deflected by about 9mm. That leaves 3mm of clearance between the head of the screws in the strut mount and the top of the top hats. On compression with a sharp or harsh bump, if the rubber bushing deflects an additional 3mm, there will be contact with the top of the top hat, and it will chirp.

I am now convinced that this is the problem (at least in my car). This explains the scuffs in the top hat, which perfectly match the shape of the heads of tbe screws, and the math works, and my problem has not recurred for two days now even though I keep hitting bumps trying to make it recur. As far as I'm concerned, problem solved, and not a KW problem. And otherwise I love my KWs...

Pics below.