It means 75% of the tread as measured from the centre on each side so for example if the tyre was 8 inches wide, it means that there would have to be at least 1.6mm tread for three inches on the left and three inches on the right of the centre of the tyre.
Or put another way, in that case (8" tread width), the outer one inch of tread on both sides of the tyre would be disregarded and everything inside it (i.e. the central 6" width) would need to have at least 1.6mm tread.
Originally Posted by Nissan doctor
It also says "The tread pattern means the combination of plain surfaces and groves extending across the breadth of
the tread" So if there is any smooth parts of the tyre then it will fail.
Don't agree, that is an explanatory sentence which does not describe pass/fail criteria.