The problem with the wheels is the wheel nuts are aluminum and in reality should be changed each racing season. The S1 & GTN is between 16-19 years old and most people have never changed the wheel nuts. The aluminum threads deteriorate over time. It seems that tightening to 400nm then means that the nut isn't always lined up perfectly with the cut out in the hub for the grub screw. I have recently replaces all 4 wheel nuts and would suggest anyone keeping their car for a long time consider doing the same. It is a cheaper option than repairing wing damage if a wheel comes loose and cheaper than switching out to non centre-lock wheels.
