Engineering a notched belt is a balancing act among flexibility, tensile cord support, and stress distribution. Precisely formed and spaced notches help to evenly distribute tension forces as the belt bends, thereby helping to prevent undercord cracking and extending belt life.
Like their synchronous belt cousins, V-belts have undergone tremendous technological development since their invention by John Gates in 1917. New synthetic rubber substances, cover materials, construction methods, tensile cord advancements, and cross-section profiles have resulted in an often confusing selection of V-belts that are extremely V Belt application particular and deliver vastly different levels of performance.
Unlike flat belts, which rely solely on friction and will track and slide off pulleys, V-belts possess sidewalls that fit into corresponding sheave grooves, offering additional surface and greater balance. As 
belts operate, belt pressure applies a wedging push perpendicular with their tops, pushing their sidewalls against the sides of the sheave grooves, which multiplies frictional forces that permit the drive to transmit higher loads. What sort of V-belt fits into the groove of the sheave while operating under pressure impacts its performance.
V-belts are manufactured from rubber or synthetic rubber stocks, so they have the flexibility to bend around the sheaves in drive systems. Fabric materials of various types may cover the stock material to provide a layer of safety and reinforcement.
V-belts are manufactured in various industry standard cross-sections, or profiles
The classical V-belt profile dates back to industry standards created in the 1930s. Belts manufactured with this profile can be found in a number of sizes (A, B, C, D, Electronic) and lengths, and are widely used to displace V-belts in old, existing applications.
They are used to replace belts on commercial machinery manufactured in other areas of the world.
All the V-belt types noted over are typically available from producers in “notched” or “cogged” variations. Notches reduce bending tension, allowing the belt to wrap more easily around small diameter pulleys and permitting better heat dissipation. Excessive warmth is a significant contributor to premature belt failing.
Wrapped belts have an increased resistance to oils and extreme temperature ranges. They can be utilized as friction clutches during set up.
Raw edge type v-belts are better, generate less heat, enable smaller pulley diameters, enhance power ratings, and offer longer life.
V-belts look like relatively benign and basic pieces of equipment. Just measure the top width and circumference, find another belt with the same measurements, and slap it on the drive. There’s only 1 problem: that strategy is approximately as wrong as you can get.