Today’s Vocabulary Lesson: Common Tire Terminology

So, do you have some chunking around your tread rib? Or a bulging carcass? Most of us have a pretty good understanding of how tires work and how to tell when they need to be replaced, but there are dozens of words that have a very specific and unique meaning when used to describe tires. Some you may have heard. Others, maybe not.

Even though you may feel like you know everything you need to know about tires, understanding these terms can give you a much better understanding of your tires – and a little knowledge certainly can’t hurt. With that in mind, let’s take a look of some of the more common tire-related terms and their meanings.

Bead: The part of the tire that is made with steel wires, wrapped or reinforced by ply cords and that is shaped to fit the rim.

Bead Separation: This is the breakdown of the bond between components in the bead.

Bias Ply Tire: A pneumatic tire in which the ply cords that extend to the beads are laid at alternate angles substantially less than 90 degrees to the centerline of the tread.

Carcass: The tire structure except tread and sidewall rubber which, when inflated, bears the load.

Chunking: The breaking away of pieces of the tread or sidewall.

Cord: The strands forming the plies in the tire.

Cord Separation: The parting of cords from adjacent rubber compounds.

Cracking: Any parting within the tread, sidewall, or inner liner of the tire extending to cord material.

Groove: The space between two adjacent tread ribs.

Innerliner: The layer(s) forming the inside surface of a tubeless tire that contains the inflating medium within the tire.

Non-pneumatic Tire: A mechanical device which transmits, either directly or through a wheel or wheel center member, the vertical load and tractive forces from the roadway to the vehicle, generates the tractive forces that provide the directional control of the vehicle and does not rely on the containment of any gas or fluid for providing those functions.

Open Splice: Any parting at any junction of tread, sidewall, or innerliner that extends to cord material.

Ply: A layer of rubber-coated parallel cords.

Pneumatic Tire: A mechanical device made of rubber, chemicals, fabric and steel or other materials, that, when mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the load.

Radial Ply Tire: A pneumatic tire in which the ply cords that extend to the beads are laid at substantially 90 degrees to the centerline of the tread.

Reinforced Tire: A tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire.

Rim: A metal support for a tire or a tire and tube assembly upon which the tire beads are seated.

Sidewall: That portion of a tire between the tread and the bead.

Tread: That portion of the tire that comes into contact with the road.

Tread Rib: A tread section running circumferentially around a tire.

Weather Side: The surface area of the rim not covered by the inflated tire.

 That’s just a small sample of the many words used to describe different tires and their components. I’m sure many – if not all – of them were already familiar to you. It’s not a bad idea to review the definitions, though, even if you already know all about tires.

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