Tire Casing

A tire’s casing is the main body and structure of the tire and is generally constructed of one or more layers (referred to as “plies,” and often described with a thread per inch, or “tpi,” count) of a woven cloth material that are covered in rubber to hold it all together, seal in air, and offer some abrasion resistance.

Standard: A tire typically with 60-320tpi and is normally standard for road bikes

Reinforced: A tire typically with a 60-120tpi with an added casing construction such as soft plastic or hard rubber insert. For MTB you will commonly see EXO or EXO+

Down Hill or Double Ply: A tire typically with 60-120tpi but with dual-layers (or dual-ply). DH Casings can also have a butyl insert to add to stablity.

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Tire Width

Tire width can be found on the side of your tire. It can be displayed many ways: ETRTO, French (metric), or English (imperial)

Below you can find a link to an ETRTO Chart with its conversions if you are having trouble finding your tire width.

How to locate width:
If using ETRTO, French or English measurements the with will be displayed differently Here are some examples:

ETRTO: 25-622 = 25mm (or 1 inch)
FRENCH: 700 x 28c = 28mm (or 1.10 inch)
ENGLISH: 29 x 2.25 = 2.25inch (or 55mm)

Practical Examples:
MTB: 29 x 2.3 indicates a tire with a 29" outer diameter and a 2.3" width
ROAD: 700x25c indicates a tire with a 700mm outer diameter and a 25mm width.

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