I remember you saying that the newest tyres on a car should be fitted to the rear wheels. Recently, in monsoon rain, my rear tyres lost grip on a corner at 30mph and the back of the car tried to overtake the front. I had a lucky escape, with just lots of grass and mud along the nearside of the car. The tread depth on one rear tyre was 3mm, the other was 5.5mm. Despite its remaining tread being almost twice the legal minimum, I have replaced the more worn tyre. A lesson learned.