There are little rubber hairs that you see on every new tire. Technically, they are called vent spews, which gives away their purpose for being on the tire. Many people think these hairs play a role in noise reduction or indicate wear but their primary purpose is air ventilation.
Those little rubber hairs are a byproduct of tire manufacturing. In a tire mold, rubber is injected and air pressure is used to force the liquid rubber into all the nooks and crannies. In order for the rubber to completely fill the mold, small pockets of air need to be able to escape.
There are small vent holes in the mold so trapped air can find a way out. When the air pressure forces the liquid rubber into all the orifices, a tiny bit of rubber makes its way out of the vent holes as well. These rubber bits firm up and remain attached to the tire when it's removed from the tire mold.
Though they serve no purpose in your tire’s performance, the tire hairs' presence is an indication that a tire is new. Tires that have been in service for some time, coupled with environmental effects, will eventually wear off the hairs.
This article originally appeared on YourMechanic.com as Why Do New Tires Have Rubber Hair on Them? and was authored by Jason Unrau.