Today I had a call from the garage doing the work on my car to say that all four Nokian zLine tyres on my car had worn through to the canvas on the inside edge!

I thought it unlikely as I had removed them all when doing the shock absorber change four weeks ago and they were fine then. I say that because I had all the wheels off the car and I had carefully inspected them for small stones and so I had slowly inspected the outside. As it was the weekend before the Saab National I also washed the wheels and dried them. I cannot believe that I missed any damage like this.
So, if all four tyres were "OK" four weeks ago and less than 500 miles later they were destroyed, what is going on?
The rear springs and shock absorbers were changed a month ago before the Saab National.
The damage was found by the garage doing the front struts and springs today.
All four have lost the inside edge. The tyres are assymetric and marked "Inside" & "Outside"
All four have been properly inflated all the time. The Tyrepal monitor will bleep if the pressure drops.
The tread on all four is legal - only just on the front and with 4mm on the rear.
The front pair and rear pair were bought at different times about 8 months apart.
The damage to all four is similar



Tomorrow will involve a close check of all sorts of things by me, but I'm not sure where to start looking, unless it's a manufacturing fault. But on two different batches?