Picked the new car up yesterday and whilst having a good look around it after getting it home I had a look at the tread depth on the 235 & 255 Continentals fitted to it. I was surprised to find that they only had 7mm of tread, I checked the rear tyre depth on my wife's car (probably done about 8000 miles ) and they were showing just over 7mm. I always thought that new tyres had about 8-9 mm , is there a standard or are they all different ???