Why Do Tires Have Grooves and Rubber Hairs? The Science Behind Tire Design

Ever wonder why tires have grooves in them? Let's make sense of it with science.

A tire's grooves help create friction between the road and the tire's tread so they can grip each other. On dry clear days creating friction isn't as necessary but on stormy nights it's crucial.

To understand why tire grooves are important, take a look at the image below:

On this perfectly smooth tire, all the water on the road will form a film between the road and the tire. This film will lift the tire away from the road. Since there's no friction, the tire will lose its grip or hydroplanes and you will lose control which can lead to serious accidents.

Now take a look at this brand new tire with grooves:

Notice there are both thin and thick grooves on this tire. As we roll along, those thinner grooves pull the water up from the road surface and the surface water ends up in the thicker grooves. As the tire rotates, our groove tosses that water behind it. This cycle repeats itself over and over again, in fact we're channeling about 3.7 liters of water per second! As these grooves lift water off the road and away from the tire, they're allowing the tread to touch the ground which in turn creates friction so the tire can grip the road. And that's why tires have grooves.

What are those rubber hairs on a new Tire?

If you ever took a close look at new tires, you might have noticed rubber hairs on the tire sidewall or tread, these are called vent spews. When tire manufacturers produce tires they inject rubber into molds, the mold's design has small holes all around in order to ensure adequate ventilation and eliminate the possibility of air bubbles getting trapped where they don't belong. As a result, when the rubber is being stretched out into the mold, some excess rubber seeps through these tiny holes and hardens as it cools. And this is essentially how tires or vent spews come to be.

Although most believe that vent spews are useless, they can actually be helpful during the manufacturing process. The quality inspectors can rely on them as a visual aid for quality control, the presence of vent spews means that the ventilation during the molding process is working correctly and the Machine vents are not clogged.

Nearly all new tires in the market today have vent spews, however, this doesn't mean that tires are created equally across different brands. Depending on differences in the manufacturing process, some tires will have more vent spews than others. So that brings us to one of the most frequently asked questions: Should you remove those little hair extensions from your tires?

In theory it's possible, but there is actually no functional reason for doing so. Some people might prefer to remove them for aesthetic purposes.

Conclusion

The grooves in tires are essential for creating friction and preventing hydroplaning, ensuring safety in various driving conditions. The rubber hairs, or vent spews, on new tires serve a crucial role in the manufacturing process, aiding in quality control and ensuring proper ventilation during molding. Together, these features highlight the intricate design and engineering behind tires, emphasizing their importance in vehicle safety and performance.