Tyre tread depth: How to measure and when it's time for new ones
Tread depth is one of the most important safety features of your vehicle. Yet most drivers ignore it until a police officer or an STK inspector raises the alarm. Learn to check the tread yourself. It takes just minutes.
What is the plenum and why does it matter?
The tread consists of grooves and protrusions on the tyre surface. Its primary function is to channel water away from the contact patch, without a tread, aquaplaning would occur in rain, meaning the tyre loses contact with the road and the vehicle becomes uncontrollable.
Tread depth directly affects braking distance. On a wet road surface, the difference between a tyre with 8 mm and 2 mm tread can mean a braking distance up to 15-20 metres longer at a speed of 80 km/h. That is the difference between stopping safely and an accident.
Legal minimum tread depth in the Czech Republic
Warning: The statutory minimum of 1.6 mm is an absolute minimum, in practice, it is recommended to replace tyres already at 3 mm (summer) and 4-5 mm (winter). At 1.6 mm the safety margin is minimal.
How to measure tread depth: 3 methods
Tread depth gauge (most accurate)
A special plastic or metal gauge is available at every car service centre for 50-150 Kč. Insert the gauge into the tread groove and read the value in millimetres. Measure at several points on the tyre, wear is often uneven.
Coin test (practical orientation)
Simple but less accurate. Use coins as a rough indicator:
- 2 Kč The coin's edge corresponds to approximately 2 mm: if not visible, the tread is good.
- 1 Kč The edge corresponds to approx. 1.5 mm, close to the legal minimum, time to act.
Wear Indicators (TWI)
Every tyre has wear indicators in the tread grooves, small protrusions at the bottom of the groove set at a height of 1.6 mm. If the tyre surface and these protrusions touch, the tyre is at the legal minimum. Look for the triangle symbol or the letters TWI on the sidewall. They indicate exactly where the protrusions are located.
Tread wear and driving style
The rate of tread wear is highly individual. It depends on driving style, road surface type, vehicle weight and the quality of the tyre itself. As a general rule: aggressive driving and frequent braking multiply the rate of wear.
Reference tyre lifespan table
| Vehicle type and driving style | km/year | Lifespan (years) | Total km |
|---|---|---|---|
| City, smooth ride | 10 000-15 000 | 4-6 years | 50 000-60 000 |
| Mixed driving (urban and motorway) | 20 000-30 000 | 3-4 years | 50 000-70 000 |
| Active driving, sporty style | 25 000-40 000 | 2-3 years | 40 000-60 000 |
| Extension / freight operation | 50 000+ | 2-3 years | 80 000-120 000 |
* Indicative values. Always measure tread depth physically, tyre age and visual condition are secondary indicators.
Uneven wear: a sign of a problem
If the tyre wears unevenly (more on one edge, or in alternating patterns), this indicates a technical issue, incorrect wheel alignment, imbalance, or a fault with the dampers. Uneven wear is reason to visit a service centre and have the vehicle inspected.
That is why it is recommended tyre rotation every 10,000-15,000 km, moving the wheels from the front to the rear axle and vice versa ensures even wear and extends the life of the set.
When to start planning the replacement?
Do not wait until the legal minimum is reached. At 3 mm (summer) and 4 mm (winter), there is still sufficient tread depth, but it is time to start planning the purchase of new tyres. Buying tyres under pressure (when a tyre needs immediate replacement) tends to be more expensive and offers a more limited selection.
The tyres are in good condition; check them regularly.
Request new tyres, book a replacement.
The boundaries of law and safety. Act immediately.
Age of tyres: an often overlooked factor
Rubber ages even when the car is not driven. Manufacturers recommend replacing tyres no later than 10 years from manufacture, regardless of tread depth. You can determine the age from the DOT code on the tyre sidewall: the last four digits indicate the week and year of manufacture (e.g., 3422 = 34th week of 2022).
Check tyres older than 6-7 years with particular care - look for cracks on the sidewall and in the tread grooves. Ageing rubber is dangerous even if the tread appears sufficient.
Time for new tyres?
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