Tires: when to really change them (and not wait for someone to tell you)
Most drivers know that tires have a legal tread limit: 1.6 millimeters. It’s the minimum required by European regulations to drive, and below that threshold the car won’t pass the MOT. What isn’t so clear in many people’s minds is that this limit has nothing to do with safety. It’s the legal minimum to avoid being fined, not the point at which the tire stops working properly. That threshold comes much earlier.
Understanding the difference allows you to make the decision to change your tires at the right time, without waiting for someone at the workshop to tell you about it or risking reaching the legal limit without knowing it.
The tread: when 1.6 mm isn’t enough of a criterion
The tread on a tire—those grooves you see in the tread band—has a specific function: to expel water between the tire and the asphalt when it rains. Without those grooves, or with very little depth, the water has nowhere to go and the tire loses contact with the ground. This is known as aquaplaning.
At 1.6 mm depth, that water evacuation capacity is minimal. Road safety studies and most tire manufacturers recommend changing them when the tread reaches 4 mm under normal conditions, and 3 mm as an absolute minimum before the rainy season or in areas with harsh winters.
To check it without instruments, there’s a quick method: insert a 1-euro coin into the main groove of the tire with the edge facing inward. If you can see the golden outer band of the edge, the tread is below 3 mm and it’s time to consider changing. If the band stays hidden, there’s still margin.
The tires themselves include wear indicators—small protrusions at the bottom of the grooves—that become flush with the surface when the tread reaches 1.6 mm. If those indicators are visible, the tire has already reached the legal limit.
Uneven wear: when the problem isn’t the tread
There are situations where the tread still has sufficient depth but the tire still needs attention. Uneven wear is the most important sign that many people ignore.
If the tire is more worn on the edges than in the center, it usually indicates insufficient pressure: the tire works deformed and presses more on the extremities. If it’s more worn in the center than on the edges, it’s normally excessive pressure. And if wear is greater on one side than the other, the problem is usually alignment or suspension geometry.
These wear patterns don’t just affect the tire itself: they’re symptoms that something else in the car isn’t right. Ignoring them accelerates the wear of the new tire you put on later, and can also affect steering and stability.
Checking the condition of the tires—not just the tread, but also the wear profile—should be done every time the car goes to the workshop, even just in passing.
The manufacturing date: the data almost nobody looks at
A tire can have sufficient tread and still be in poor condition. Rubber ages even if the tire doesn’t roll, and after a certain age it loses elasticity, cracks appear on the sidewall, and its grip capacity reduces, especially when wet.
The manufacturing date is printed on the tire’s sidewall as a four-digit code inside an oval: the first two digits indicate the week of the year and the last two, the year. A tire marked with 2419 was manufactured in week 24 of 2019.
Most tire manufacturers and road safety bodies recommend inspecting tires starting at five years from manufacture, regardless of visual appearance, and replacing them at ten years maximum even if they look in good condition. A ten-year-old tire with intact tread is not a tire in good condition: it’s an old tire with little use.
This is especially relevant for cars that cover few kilometers per year—second home cars, vehicles used mainly in summer—where wear from use never reaches the tire but rubber aging advances anyway.
Seasonal tire changes: when it makes sense and when it doesn’t
In much of Spain, the summer/winter debate isn’t as relevant as in central and northern Europe. Summer tires work well in most of the peninsular territory throughout the year, and all-season tires easily cover the mild winters in most of the country.
But if you live in a mountain area, if you regularly cross mountain passes in winter, or if the car will be exposed to temperatures frequently below seven degrees, winter tires stop being an exotic option and become a real difference in behavior: the rubber compound is formulated to stay soft in the cold, which improves grip on wet roads in cold, in mud, and in snow.
The practical rule for seasonal tire changes is: winter tires when temperatures drop consistently below seven degrees, and back to summer when they rise steadily above that threshold. In the Northern Hemisphere, this usually translates to changing around October-November and back in March-April, though it depends a lot on the area.
Keeping track
Tires don’t have a fixed change interval in kilometers or months. It depends on driving style, type of road, pressure maintained, whether the car is properly aligned, and climatic conditions. That’s why inspection has to be periodic and visual, not based solely on a predetermined number.
What is worth recording: the date when your current tires were fitted, the tread depth they had when fitted if you measured it, and the manufacturing date that appears on the sidewall. With that data, at any inspection you can know exactly where you stand—both in terms of wear and age—without depending on someone at the workshop to tell you, or being told when there’s little margin left. If you use OwnAutoCare for your car’s history, it’s the natural place to also note your tire change: date, kilometers, and tire reference if you have it.