Advice Fact List

Advice: Why your choice of car tires is so important

**One of our readers wanted to write an article in his area of expertise, which we are really happy to present.**

Most drivers know to look after their car, but few people put any real thought into why this is so important. Your car tires, specifically, are a great example. They are responsible for a great deal of your car’s driving capabilities and performance, yet most people don’t consider this when shopping for new tires.

If you’ve ever wondered just why tires are so important, here’s a look at how they influence your vehicle.

The Contact Patch

When you think about it, your tires are the only part of the car that (well, should) make contact with the road surface. No matter how good the engine is or how well designed the overall ride is, none of this matters if the tires aren’t precisely designed to offer the right driving parameters.

How effective would braking be, for instance, if the tires offered no grip? Likewise, how fuel efficient would your car be, if these products were not designed to reduce the various drag forces tire’s face? This includes aerodynamic drag, as well as the pneumatic trail – a force created by the tire rolling.

Of course there is also the question of friction between the tire and the ground. As you will see, this is one of the many important factors that tire designers have to take into account, as it is often a question of striking the right balance between various different characteristics.

The Tread

As we just mentioned, the contact area is vital. This means the tire tread – the part of the tire designed to make contact – is just as crucial.

Direction Patterns

Different tread blocks and patterns have different properties. Directional patterns offer excellent traction, making them useful in winter. Similarly, asymmetric tires mix larger tread blocks on the outside (for traction) and smaller blocks (for wet grip) on the inside, along with sipes for redirecting water. This offers a balance between dry and wet performance, while other tire patterns (such as directional tires) may choose to specifically favor one condition. Of course, when tires have different directions and sides, this means you have to fit them in the correct manner to make the most of their beneficial properties.

Directions Tire Treads

Similarly, tires also incorporate various grooves and sips into their treads. These are designed to expel water to prevent aquaplaning – when this occurs, the water creates a layer between the tire and road, causing the car to ‘float’. It is these little details that ensure smooth, panic-free driving.

Winter Tires

Winter tires often feature more grooves and sipes to remove water.

Tread Depth

Finally, you also need to keep an eye on the tread depth. More than just obeying the legal minimums in your country, a tire that is worn down loses some of its properties. Grooves become more shallow and less efficient, for example, while a completely worn down tire has no tread blocks or sipes at all.

Worn Out Tires

 

Tire Size

Tire Size

Likewise, the tire size is also important. A bigger tire offers a bigger contact patch, again changing how the car handles. Narrow tires, for instance, offer better grip, while a wider tire dissipates the pressure and weight from the vehicle. While the latter offers less grip, it makes it better on uneven surfaces, such as snow and slush.

In fact, more experienced drivers occasionally change their tire size to improve certain criteria. Of course, this can also have a negative impact on other areas, so it is always advised to stay with the recommended size for your vehicle, as indicated by the manufacturer in the manual or via an online tire size calculator.

Tire Pressure

Tire Pressure

Finally, it should be clear by now that a lot of effort goes into designing tire products, with the shape and size of the tire being a key issue. This also means that, as the driver, you have to maintain the tire in this shape and quality, which is why tire pressure is also vital.

A tire that is overinflated, for instance, will strain the tire material and cause the tire to be too large. This stiffness will actually reduce the contact area, causing excessive wear in the middle. It also cannot handle rough surfaces and irregularities in the road as well. With enough air pressure, they are also more susceptible to damage.

On the other hand, an underinflated tire can’t maintain its intended shape, defecting and bending as it rolls. This makes the car less fuel efficient and difficult to steer precisely. Just like overinflation, this can also cause excess damage, as the change in shape causes different parts of the tire to make contact with the ground.

Fortunately, car tire pressure is easy to check, but you should do so on a regular basis. The heat, both when driving and during particularly hot weather, can cause changes in air pressure, As a result, you should always check your tires when they are cold, as this is what the recommended values (again, determined by your manufacturer and found in your car manual) are quoted for.

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About the author

Giles Kirkland

Giles Kirkland is a professional mechanic with a passion for sharing information with other drivers. When he’s not working in the garage, he enjoys taking his current car out for a drive.

9 Comments

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  • Sorry if this sounds harsh but the site admins should remove this article.

    “Narrow tires, for instance, offer better grip” no they don’t.

    “the latter (a wider tire) offers less grip … it makes it better on uneven surfaces, such as snow and slush”

    Narrow tyres cut through pools of water better and will grip the ground below a deep puddle better if the grooves do not redirect the water fast enough preventing aquaplaning but that is the only time that occurs. Wider tyres provide more surface area and with that more grip. If there is tarmac below the slush, you want narrow tyres, if there is not then you want wide tyres.

    I’m surprised you haven’t mentioned rubber types and winter vs summer tyres.

    Some of this info seems to have been misinterpreted from stuff read elsewhere and no-one should rely on the info in this article which is at best incomplete and in some cases dangerously misleading. I wish this site wouldn’t do any articles on safety stuff they don’t really understand.

    • Narrow tires offer better grip, YES, they do. Wider tires are only better for soft or loose surfaces that skinny tires would tend to dig down into. I am not talking city driving though. Anything will get you across town..

      • Ahhhhh no. No no no. As a general rule, wider tyres will offer more grip in the majority of driving conditions on surfaced roads.

  • I don’t completely understand why a car manufacturer knows how much pressure should be in the tire, when the max pressure is written on the side of the tire and varies from tire to tire.

    • The tyre manufacturer prints the maximum pressure that the tyre can handle, not the recommended tyre pressure. It is there so that you don’t use a tyre with a max of say 35 psi in an application that requires 40 psi. You can actually take a decent car tyre up to about 10 times that before it will break the tyre or wheel (yes the metal of the wheel will break first in some cases). The car manufacturer knows the weight of the car which is pressing down and changing the contact area. The tyre manufacturer does not because the tyre could be used on many different cars. Some will have very different weights and most will weigh more at one end than the other (engine weight). Long story short, trust the car manufacturer recommendation, the tyre company are giving you maximums, not recommendations. If you are treating them as recommendations then your tyres are probably dangerously over inflated.

  • There is also the point, not mentioned, about specific ratings tires have, be it speed load. Those are also important things to consider as well.

  • I really feel you should have gone more in depth on various topics, including winter tires. People just don’t seem to realize how beneficial they can be. Most people think a tire is a tire.

  • Thanks for sharing your thoughts about why the choice of car tires is important. I liked that you mentioned that different tread blocks and patterns have different properties. I never knew that there are different tread designs for tires and that they do have a significant role. I’d make sure to check out my car’s tires and do some replacement if needed.

  • As can be seen by the formula pressure=force/contact area, the contact area does not depend on the tyre size, but only on the tyre pressure and the load (part of car weight) on that tyre.
    The grip force doesn’t depend on the contact area, it only depends on the material pairing rubber – tarmac (tribological factor), as long as there are no fluids in between. So it doesn’t depend on the car’s weight ( a frequent misunderstanding) , which can be seen with the formula of the 2 concurrent forces when driving in a curve:
    u x m x g = m x vxv / r,
    u tribological factor
    m weight load
    g earth’s gravity factor
    v speed
    r radius of the curve.
    I.e. the weight can be eliminated on both sides, it doesn’t influence the grip.

    This is a simplified theory of course, in reality some preconditions may be failing, e.g. the tribological factor may be slightly dependent on the contact area, i.e. may be not perfectly linear etc.

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