Essex Ford Basildon

Video of dread depths varied from 5.3mm to 5.8mm (which I though was odd) when I collected the car all measurements had been rounded down to 5.00mm. The vehicle health report put tyres into amber, with the comment ( four items will need attention in the near future) when I queried this I was told that they always round down to the nearest millimeter as a safety precaution, which I believe to be fraudulent. I took the car for a second opinion and with the wheels off the car all four measured 6.0mm evenly accross all four tyres.I have that report and photos of each tyre with the measurements. I have informed Essex Ford of this, and am awaiting thier response