What are those string-like treads on bicycle tires?

I was wondering what those little rubber things that look like cut off strings are that stick out of new bike tires and tend to wear off.

Someone told me that they provide traction? Thank You

 

Probably not...

 

Well, they probably provide a tiny bit of traction until the wear off. They certainly don't make the tire any slicker.
But that's pretty much unintentional. Strictly speaking, they are "accidental" remains from the molding process.

 

They are called "mold sprues"...and about a dozen other names.

They serve as gas vent paths to insure full mold filling. As liquid polymers (rubber) are forced under injection pressure or mold vulcanization, air and gases produced by the molding process must exit the mold. It does so thru spues and vents located around the circumference of the mold cavity.

The molding machine operator, upon extracting the finish molded tire from the mold cavity, can quickly inspect the product for full mold fill by checking for the presence of the sprue nubs...AKA as tits, whiskers, hairs, etc.

In other casting or molding industries they may be termed mold risers.