Casing thread density is measured in threads per inch (one inch=25.4 mm), and known as TPI. The casing is the heart of the tire or tubular and is made of rubber and threads (which may be nylon, cotton, Kevlar, or Corespun).

Standard road tires usually have casings of 24–55 TPI. Vittoria tires and tubulars range from 26 TPI to 320 TPI. Riders in search of higher performance are likelier to choose higher-TPI tires.

For many sporting riders, folding tyres of around 150 TPI are a good all-round compromise of weight, rolling resistance, durability, and comfort. A higher TPI brings the benefit of lower weight and rolling resistance, but at a penalty to durability. Regardless, riders aiming to play harder will usually seek out tubulars and open tubulars with a TPI of 200 or greater.