3 Reasons Why Sports Cars Have Thin Tires
Thin tires are common in high-end cars. Modern ones manage to make the wheels more noticeable while preserving their mechanical resistance. But do you know how that all happens?
Automotive tires are produced and marketed according to key dimensions: tread width, sidewall height, and rim diameter. Even though they are all independent, commercial tires are usually available in some specific combinations of them.
Each variable is capable of making big changes to the car's dynamic behavior on its own, so they would deserve individual analyses. This time, we are only considering the sidewall height, that is, the radial distance between the tire's outer and inner diameters.
The current convention is to express this magnitude as a percentage of the tread width. For example, if the tire code is 225/45 R17, the tire's tread is 225-mm wide and the sidewall height is 45% of that, which makes roughly 101 mm. The "17" represents the rim diameter in inches.
Why Do Sports Cars Have Thin Tires?
#1: Makes the Ride More Controllable
#2: Makes Rims More Noticeable
#3: Accommodate Large Wheels
Are Thin Tires Only for Sports Cars?
What are the Cons of Thin Tires?
Sports cars have thin tires, mostly because it makes the ride more controllable. Because the thin tires have less rubber between the rim and the ground, the car's movement becomes more direct and the body roll is reduced.
Now let's get into details.
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Thin tires change the way the wheels make contact with the ground. The car's movement becomes more direct, with reduced body roll. While some drivers complain that it makes the ride less comfortable, others enjoy this stiffer setup – especially those who drive sports cars.
In plain language, thin tires have less rubber between the rim and the round. Their sidewalls are short and, as a result, they literally offer less material to "flex" when the car is moving. In urban cars, taller tires are more convenient because they absorb the shock of a pothole much better, even offering higher physical protection to the rim.
When it comes to sports cars, their top priority is to offer the best dynamic behavior, especially at high speeds. Thinner tires don't allow so much body roll, so the ride becomes stiffer and, as a consequence, offers more control to the driver.
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Design is a key selling point for sports cars. They are heavily dependent on their image; their target buyers want them to impress, whether in movement or stopped. Therefore, it is important that they have beautiful rims, among other items, and that the rims are easy to notice.
In a car, it is impossible to see rims and tires separately. They have similar shapes and always work together, so our look tends to bundle them. What automakers can do in this regard is to change each one's size independently, considering that there is a limit to the outer diameter – this part is explained on the following topic.
In practice, the larger the wheels are for a fixed outer diameter, the more noticeable they are. The only way to do that while respecting the outer diameter is to use thinner tires.
"Taller" tires, that is, tires with a taller sidewall, are only useful in other types of cars because they have different requirements for their dynamic behavior.
Cars offer limited space for the wheel. The overall diameter is limited by the body's design. The gap between wheel and body makes the car less aerodynamic, so automakers make it as small as possible. Those are all technical reasons favoring thin tires.
The previous topic shows that it is important to put the rims in evidence. However, they cannot grow indefinitely, primarily because they have to fit into their designated areas of the body, named wheel wells. That is a physical limit defined in the early stages of the car's project development.
The other reason is that, regardless of the available room, it is important to make the whole wheel fit inside the well with a small gap. This gap produces a deviation of air flow which was supposed to go smoothly throughout the car's body, which means it makes the car less aerodynamic. The larger that gap is, the more harmed the car's design will be.
The only way to use large wheels in a limited well space is to make the tires as thin as possible while still meeting their performance and resistance requirements.
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Even though they are recommendable almost only to them, the concept can be extended, indeed, to other models. City cars can also use thin tires, as long as we understand what those changes imply to the car's dynamic behavior.
Since we are only considering the height of the sidewall, let's set all the other dimensions constant for this analysis – diameter, width, etc.
Choosing thinner tires reduces body roll and makes the ride stiffer but easier to control, especially at high speeds. This change can be desirable even in the typical driving conditions of a sedan or a hatchback. The driver must only avoid choosing excessively thin tires because they would cause a drastic change and wouldn't even look so good.
The only models which should avoid thin tires in all cases are commercial and off-road cars. Both are designed to work under heavy load, whether static (objects in a van, for example) or dynamic (an AWD car bouncing and skidding on a dirt track), so they need as much support as they can. Their suspension is prepared for such a task, of course, but the tires provide a different type of support that cannot be neglected.
If you keep the same rim diameter, thinner tires will reduce the outer diameter of the wheels and make the car both uglier and slightly less aerodynamic. Besides, the whole ride loses comfort because the car will have a smaller capacity to absorb low impacts, such as those of potholes.
According to the previous topic, drivers should be careful when changing tires for thinner ones in city cars. If it's not done with professional advice, that will make them less comfortable to the point of altering their driving dynamics.
Commercial and off-road models, in turn, should avoid them altogether. Thin tires would simply be counterproductive because the changes they provide go against the purposes of those cars.
Thinner tires would make vans and pickup trucks suffer more when carrying heavy loads because the tires would have less material with which support them. Off-road vehicles, on the other hand, would be more exposed to damage from severe driving conditions because of that and would absorb ground imperfections much worse.