With tread depth, it’s easy to tell if your tyres need replacing or repairing. It comes down to maths. In Europe, passenger vehicles, with fewer than eight seats, require a legal minimum depth of 1.6mm across 75% of the tyre’s width and 100% of the tyre’s circumference. This is also true of goods vehicles and light trailers not exceeding 3,500kg max gross weight.
Most vehicles that are larger, and motorbikes 50cc and over (with or without a sidecar) the legal minimum is 1.00mm and for mopeds and motorbikes under 50cc the original tread pattern must be visible.
In the USA, the minimum tyre tread depth is 3/32".