Tires tell us through their uneven wear, did you know that?

Summer is here and it's time to get on the road with our car, family, luggage and, of course, beach toys. We should always have our car ready, but it's true that we worry more when we're going on a trip of several hundred kilometres.

If it's been several months since your car's service, it's a good idea to take it back to a garage so the experts can give it a thorough check and make sure it's ready for that family trip. Even if the service was recent, you shouldn't take it lightly. Check the basics yourself, such as fluid levels (oil, coolant, windshield washer fluid, etc.), tire pressure ( don't forget the spare tire) , and the overall condition of the tires.

Today we're going to focus precisely on this last point: what a tire tells us at first glance. But we'll go beyond just how close the wear indicator is to the maximum permissible limit, examining and explaining the different types of uneven wear that can appear . I think it goes without saying that tires, along with the braking system, are the most important part of a car.

Ideally, a tire should wear evenly across its entire tread. This means that the tread, the part that makes contact with the road, should wear down uniformly, without showing premature wear on either side, both sides, or in the center of the contact patch.

However, this isn't always the case, and we might find that our tire is closer to the wear indicator (the wear indicator) in one area than another. In most cases, this is due to an alignment problem , more commonly known as wheel alignment, or incorrect tire pressure; although it could also be due to a defective tire or very demanding driving style for tires that aren't suitable for high-speed driving.

Wear due to poor tire pressure

I'm sure most of you, dear readers, know how high or low air pressure affects a tire, but let's do a quick review.

• If they wear out more quickly on the sides This means that the pressure is lower than it should be. When the tyre is underinflated, it becomes “flattened” and does not rest as it should, causing the tyre's shoulders to touch the ground. This also contributes to higher fuel consumption and possible overheating of the rubber, which will result in even greater wear.
• On the contrary, if Premature wear appears in the central area of the tread, it means that the wheel is overinflated. When the central area is more inflated, it expands and, therefore, the ends of the tread have much less contact with the ground, which causes the central part to wear down. This will cause us to lose grip.

We mustn't forget that when we go on vacation, there are usually several people in the car and the trunk is full, so the total weight increases considerably. The car itself usually displays tire pressure readings for light loads, normal loads, and heavy loads. Remember that.

Irregular wear due to steering geometry

Abnormal tire wear isn't only caused by incorrect tire pressure. It can also be due to other factors, primarily steering geometry.

In this case, wear will affect both wheels on the same axle equally in most cases. That is, if the right wheel wears more on the right side, the left wheel will wear more on the left side (outer sides of the tread).

We don't want to explain in depth the geometry of the steering and the different dimensions that affect the parallel of a car, since that would require a separate article, which we will leave for another day. Therefore, we are going to explain it in a simple way and without too many complications.

• Greater wear on the outside: It may be due to very sporty driving, but we will leave this aspect aside and focus on anomalies that occur in normal, everyday driving. A tyre with a smaller tread on the outer side will normally be a problem caused by high convergence. To give you an idea, the wheels are always “a hair” towards the inside, as if they were trying to cross a few metres in front of the car. This is called “convergence”, and if it is excessive it causes this external wear.
• Greater wear on the inner side: We must pay attention and check, properly, the inner side of the tyre. Since it is not easily seen with the wheels straight, we may notice this problem too late. To check it, we only have to turn the wheels as far as possible and take a look. The greatest wear on the inner side of the tyre is also caused by convergence, although in this case negative, when the wheels, instead of “wanting to meet” a few metres ahead of the car, try to separate. This is known as negative convergence and also as divergence.

This phenomenon, internal wear, can also occur due to an incorrect camber adjustment . Just as the wheels are normally angled inwards in toe-in, they have a slight tilt along the imaginary horizontal axis that points them slightly towards the center of the engine compartment (on the front axle), so they make a little more contact with the asphalt on the inside of the tire. This is imperceptible in road cars, but it's clearly visible in racing vehicles.

Braking without ABS?

Finally, although it's not something you see every day, we have the infamous flat spots . This defect appeared after hard braking with wheel lock-up, and was even more noticeable when the asphalt temperature was high, i.e., in summer. Currently, and for several years now, all vehicles approved for use on public roads in Spain must have an anti-lock braking system, the well-known ABS , which prevents the wheels from flattening during sudden braking.