How do you measure tread depth?
- Use a tread depth gauge for the most accurate result and measure in the main grooves.
- Measure each tire at least at three points (inner, centre and outer) and use the lowest value.
- The small bars inside the grooves (TWI wear indicators) are 1.6 mm high. If the tread surface has worn down to these bars, the tire has reached the legal minimum.
What does uneven wear indicate?
- Wear only on the inner or outer edge: check toe and camber alignment.
- Wear in the centre: the tire may be over-inflated.
- Wear on both edges: the tire may be under-inflated.
- Cupped or patchy wear: check the shock absorbers, wheel balance or suspension.