New tires may have colored stripes around the tread and small rubber filaments on their sides or tread. The two features have different origins, and neither is a warning that drivers need to act on.
The filaments, sometimes called rubber “hairs,” form during vulcanization. As rubber is pressed into a mold, air escapes through tiny vents, carrying a little excess rubber with it. That rubber hardens into short strands. They have no function and disappear after the tire has been driven on for a few miles.
Colored stripes, meanwhile, are production codes used by tire manufacturers to help identify products and sort them in storage. They can indicate details such as the tire model or factory, and may help trace a batch if it is affected by a recall. The codes are not standardized, so their meaning varies by manufacturer. Some tires have colored dots instead, and others have no colored markings at all.
The stripes can sometimes serve as a visible sign that a tire has not yet been driven on, but their absence does not prove that a tire is used, since not every new tire has them. They are not intended as information for customers.
For drivers, the important specifications are on the sidewall. A marking such as 205/55 R17 91V indicates the tire’s width, profile, construction, rim diameter, load index and speed rating. Buyers should check these details against the tire dimensions approved for their vehicle. The sidewall also gives the manufacturing date as four digits representing the week and year.
Sources: Motorpasión.