Maintenance
How to Properly Check Tire Tread Depth
Sep 28, 2024 · 6 min read
Tread depth is the single best indicator of how much grip you have left in the wet. Learn the coin test, the gauge method and what the wear bars mean.
Tread grooves exist to move water out from under the contact patch. As they wear down, the volume of water they can clear falls sharply, and so does your wet braking performance.
The legal minimum is not the safe minimum
Most regions set the legal limit at 1.6 mm across the central three quarters of the tread. Independent testing consistently shows wet stopping distances lengthening dramatically below 3 mm, so plan replacement well before the legal limit.
Three ways to measure
Use a digital depth gauge for an accurate reading at several points across each tire. If you do not have one, insert a coin into the main groove and compare against the rim band. Finally, every tire has moulded wear bars in the grooves: when the tread sits flush with those bars, the tire is finished.
Check for uneven wear
Measure the inner, centre and outer grooves. Wear concentrated in the centre suggests over-inflation, wear on both shoulders suggests under-inflation, and wear on one shoulder usually points to an alignment issue.
