Engineering a notched belt is certainly a balancing act between versatility, tensile cord support, and tension distribution. Precisely designed and spaced notches help evenly distribute tension forces as the belt bends, thereby assisting 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 compounds, cover materials, construction strategies, tensile cord advancements, and cross-section profiles have led to 
an often confusing selection of V-belts that are extremely application particular and deliver vastly different degrees of performance.
Unlike flat belts, which rely solely on friction and will track and slide off pulleys, V-belts have sidewalls that match corresponding sheave grooves, providing additional surface and greater balance. As belts operate, belt stress applies a wedging force perpendicular to their tops, pressing their sidewalls against the sides of the sheave grooves, which multiplies frictional forces that permit the drive to transmit higher loads. How a V-belt fits into the groove of the sheave while working under stress impacts its performance.
V-belts are made from rubber or synthetic rubber stocks, so they have the flexibility to bend around the sheaves in drive V Belt systems. Fabric materials of varied types may cover the share material to supply a layer of security and reinforcement.
V-belts are manufactured in a variety of industry regular cross-sections, or profiles
The classical V-belt profile goes back to industry standards developed in the 1930s. Belts produced with this profile can be found in many sizes (A, B, C, D, Electronic) and lengths, and so are widely used to displace V-belts in older, existing applications.
They are accustomed to replace belts on industrial machinery manufactured in other parts 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 easier around little diameter pulleys and permitting better temperature dissipation. Excessive heat is a major contributor to premature belt failure.
Wrapped belts have a higher level of resistance to oils and severe temps. They can be used as friction clutches during start up.
Raw edge type v-belts are more efficient, generate less heat, allow for smaller pulley diameters, boost power ratings, and offer longer life.
V-belts appear to be relatively benign and simple pieces of equipment. Just measure the top width and circumference, find another belt with the same dimensions, and slap it on the drive. There’s only 1 problem: that strategy is approximately as wrong as you can get.