The legal minimum tread depth for trailer tyres is typically 1.6 mm across the central three-quarters of the tread, around the full circumference of the tyre, in many regions such as the UK and EU. In the United States, for commercial truck and trailer tyres, regulations usually require at least 2/32 inch (about 1.6 mm) tread depth on trailer (non‑steer) tyres.

Key legal standards

  • In many European countries (including the UK), the minimum legal tread depth for car, caravan and light trailer tyres is 1.6 mm over the central three-quarters of the tread and around the entire circumference.
  • In the US, federal rules for commercial vehicles say steer (front) tyres need at least 4/32 inch, while all other tyres (including trailer positions) must have at least 2/32 inch of tread depth.

Safety recommendations

Even though 1.6 mm (or 2/32 inch) is the legal minimum in many places, replacing tyres earlier is safer, especially for wet conditions. Many fleet and tyre specialists recommend considering replacement when tread gets down to about 3–4 mm for better grip and shorter stopping distances.

How to apply this

  • Check the rules specific to your country or region, as minimum legal depths can vary slightly and trailers may fall under different weight or usage categories.
  • Use a tread depth gauge and measure in the main grooves across the central band of the tyre, not on the shoulders, and avoid ridges or wear bars when taking a reading.

When in doubt, aim to be above the legal minimum; the minimum is a safety floor , not a target.

Information gathered from public forums or data available on the internet and portrayed here.