The Secret Origin of Tire Hairs and What They Mean

Everyone knows about the little hairs on the surface of new tires. While it’s easy to form a casual personal theory as to what they do, most of us never actually look it up. Some think they contribute to traction, while others think they contribute to noise reduction or are put there specifically to indicate wear on your tires because they go away after a while. This superstition can even cause people to think twice about buying a used car or used tires that don’t have those little rubber hairs on them. As it turns out, none of these theories are correct. In fact, those hairs don’t serve any purpose at all, they’re a harmless byproduct of the manufacturing process.

How They Got There

Tires are made by rubber injection, in which pressurized liquid rubber is shot into a tire mold. Because rubber is not water, it needs vent points to fill every crevice and detail of the mold. These vent points are tiny holes distributed around the mold and as the tire is completed, pressurized rubber is pushed through them. The result of pressurized rubber through these tiny holes are the little “hairs” we’re all familiar with. This is why people associate tire hairs with new tires, because these lightweight rubber filments wear off incredibly quickly on road surfaces so usually only brand new tires have them. However, something that most don’t realize is that freshly recapped tires also have these little hairs.

Why New and Recapped Tires Have Hairs… But Used Tires Don’t

If you’ve ever looked at a new tire and a recapped tire of the same model side by side, you may notice a few slight design differences based on the equipment of the recapper but you will also notice that both tires have the ‘new tire’ hairs. The reason for this is because recapped tires are actually fully rebuilt by filing off the old tread and using fresh rubber injection molded onto the sturdy central ring. The injection molding process includes small vents in the mold to that the rubber fills completely, which creates the exact same little hairs as when the tire was molded by the manufacturer. The reason you don’t see these hairs on used tires that have not been recapped is that they wear off over time spent on the road. This is a great way to tell the difference between ‘used’ tires, which have already had their tread worn down, and recapped tires which are on a whole new lifespan with freshly injected tread.

What the Tire Hairs Mean

While it’s true that tire hairs are created by ventilation in the manufacturing and recapping process, they are only a byproduct of production. The hairs don’t do anything and they’re not an important part of your tread. In fact, they wear off of new and recapped tires almost immediately once you begin driving. However, you can learn one thing from tire hairs, which is whether or not the tire treads are fresh. If you want to be the first person to drive on your treads, the presence of these otherwise useless little rubber filaments will tell you approximately how recently the tread was injection molded.

The truth about tire hairs that rubber injection requires vents to completely fill a mold, something that is done with both new and recapped tires. Your tire is not full of little holes, does not have a special sound reduction feature, and those hairs do not help with traction. If you’re looking at used cars or used tires, don’t expect to see the rubber filaments on the tires. However, if you’re looking for brand new tires of freshly refurbished tires ready for another 50,000 miles.

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