Why Do Tires Have Hairs? Car Experts Explain Their Purpose

Sep 23, 2023

RD.COM Knowledge

If you’ve ever looked closely at the tires on your car or touched the tires while wandering around an auto shop, you’ve probably seen those little hairs sticking out of the black rubber and wondered, Why do tires have hairs? Are they there for some safety reason I don't know about? Those little bits are one of the weird car features most people don't usually stop to think about. But then some people do.

If you’ve pondered the tire-hair question, you may have a few theories about this—and quite possibly also why there are numbers and red and yellow dots on tires as well. There are all kinds of interesting facts about your car, whether this is something that regularly takes up your brain space or not.

When it comes to the tire-hair mystery, we asked car experts to solve it for us once and for all. This will free up some mental bandwidth to think about practical tire issues, like figuring out the best time to buy tires and making sure your next car has all the safety features you want. Here's what the auto pros told us.

Get Reader's Digest's Read Up newsletter for more fascinating facts, humor, travel and tech all week long.

Located on the vertical part of the tire, which is also known as the sidewall, these curious little rubber hairs are known as vent spews or—more adorably—tire whiskers. According to Will Robbins, director of consumer product strategy for Bridgestone Americas, these vent spews are a result of the tire manufacturing process and happen as the tread pattern mold is pressed into a new tire. "Each mold is specific to the tire size and type that is being made," says Robbins. "As the pattern is pressed into the tire's rubber, the extra or unnecessary rubber requires a way to escape the mold." Because pinhole-size escape vents are created throughout each mold, little tire hairs are born.

Curiously, there's no set number of hairs each tire will have. The exact number of vent spews varies based on the design and size of the tires. But the presence of tire hair is universal. They are nothing more than remnants of the intricate process that makes strong and durable tires that safely carry you around town every day. You can now impress your friends with some random trivia knowledge.

These vent spews are crucial in the tire-making process. During the manufacturing of a tire, a process known as vulcanization occurs. This is when the raw rubber is heated and molded into the shape of a tire.

Some excess rubber will seep out through small vents or channels in the mold. As the tire cools and the rubber solidifies, these tiny strands, or hairs, remain attached to the surface of the tire. When it comes to what are the hairs on tires for, Margarette Stine, automotive expert at 4WheelOnline, says this: "They help to ensure that there are no trapped gases or air bubbles in the tire that could compromise its structural integrity and performance." You can also make sure your tires are safe with this one-second tire test.

They don't have any effect on safe driving. Because they’re found on the part of the tire rubber that doesn't hit the road, Stine says they have no impact on how well your tire grips the pavement in rainy weather or the overall comfort of the ride. These rubber hairs also don't have any impact on road noise or why your tires squeak when you’re driving. They are merely a testament to the new tire's arrival in the world.

You can if you want to, but there is no functional reason to do it—whether you’re buying the most affordable tires on the market or you recently snagged the tires that car experts buy. If you’re inclined to want to safely trim or remove them for aesthetic reasons, you can do so with extremely sharp scissors or use a fine abrasive tool to shave them off, suggests Stine.

Take caution and use great care to avoid cutting into the actual tire rubber. That can damage the structural integrity of the tire or compromise the tire's performance, which means, at best, you’ll need to shell out more money to replace a tire. It could also mean you’ll have an accident. But, says Stine, "as long as the process of removing the tire hair is executed with precision, your tire will not be exposed to unnecessary risks."

Tire hairs are one of the things you probably never thought about. But now that you’ve been pondering the question "Why do tires have hairs?" you may wonder or even feel a little nervous if you don't see them there. You probably don't need to sweat it. They are naturally worn away during normal driving, says Robbins, and the presence or absence of these hairs doesn't really determine if a tire is safe. It's far more important to regularly examine your tires for signs of wear and tear, such as reduced tread depth, cracks or bulges.

There is one instance, however, where the lack of tire hairs can be a tell: It could be a sign that they are worn, old and need to be replaced. Part of being a responsible car owner means monitoring the health of your tires closely and regularly. Refer to your car manufacturer's guidelines for when and how often your tires should be replaced. And while you’re collecting car knowledge, here's how to get better gas mileage too.

Sources: