Those little rubber hairs on a brand-new tire aren’t for extra grip; they’re by-products of the moulding process and have no intended role in driving

When a brand-new tyre is installed on a car, its outer surface may have multiple thin rubber strands. These tend to be more visible around the tyre's sidewalls and shoulders, but there are cases where one may even see them on the tread. These strands wear away as the tyre is driven, so people may assume they are meant to improve grip. That is not the case. These strands are commonly called vent spews, tyre whiskers, or sprue nubs, terminology used across the tyre industry and in tyre-mould patent literature to describe rubber that hardens inside a mould's air-vent holes during vulcanisation. They occur when raw rubber enters the small holes in the mould during the tyre vulcanisation process. The holes enable the release of any air and gases that get trapped during the process, as described in technical documentation on tyre mould venting and finishing.

The fibres do not belong to the tread pattern of the tyre; rather, they add no traction, braking capability, or stability. The strands on the tread wear off due to friction with the road, while those on the sidewall may last longer because they are not meant to touch the road surface. This rubber bristle-like pattern is simply a sign of the tyre production process, not an added traction feature.

Tiny mould vents allow trapped air to escape during vulcanisation


Tyre manufacture starts by moulding raw rubber and other components in a mould that gives the tyre its tread and sidewall shape. This mould has small vent holes that let air escape as the rubber fills the cavity. This type of vent hole is called a micro vent or pin hole vent. Some uncured rubber enters these vent holes and cures along with the rest of the tyre. A tyre-mould vulcanisation patent (US/EP filings on venting apparatus for tyre moulds) describes how unvulcanised rubber flows into vent holes after trapped air is released, forming vent spews shaped as beards that must later be trimmed during finishing, consistent with industry explanations of vent spews as a by-product of the vulcanisation process.

Rubber entering the vents forms the visible strands

The spurs on a tyre are not attached after production by workers. They are moulded directly during moulding as rubber is forced into the ventilation channels. That same rubber, initially uncured when it enters the vent, hardens along with the rest of the tyre during vulcanisation — after curing and demoulding, it often remains attached to the tyre surface, creating the protrusions seen on a new tyre. They vary from tyre to tyre because moulds differ in their ventilation systems. This means some tyres have more spews in certain areas than others.

The rubber strands do not improve the tyre’s performance on the road. They do not have anything to do with making tyres more stable or reducing their stopping distance. A tyre’s performance is determined by the properties intentionally built into it. These include the rubber compound, tread design and tyre construction. The vent spews are an incidental, though fully expected, product of the tyre-making process: engineers design the vent holes deliberately to release trapped air, but the resulting rubber strands themselves serve no functional purpose.

Tread spews wear away faster than sidewall spews

Where a vent spew appears helps determine how long it lasts. Strands on the tread are exposed to continuous abrasion from the road and thus wear away during normal driving. Sidewall strands face much less abrasion because the sidewall does not come into contact with the road. This means sidewall spews can last long after the tread spews have worn away. Their persistence on the sidewall does not mean they serve any function. They are just residues of the same moulding process that made the tyre.

Drivers do not need to remove the rubber hairs

It is unnecessary to cut, rip, or otherwise remove vent spews from a new tyre because they are harmless leftovers from manufacturing and will naturally wear away on the parts that contact the road. Their presence cannot be used to judge tyre quality because the number, length and position of vent spews depend on the mould’s ventilation system and the manufacturer’s finishing techniques.