A chainring is the circular gear with teeth that is attached to the bicycle chain in order to rotate the rear wheel. The bicycle can have anywhere from one to three chainrings depending on what use the bicycle is designed for.
The chainring size in triathlon and long-distance riding influences gears as well as how fast you can pedal. Larger chainrings have larger gears for faster riding on flats, while smaller chainrings are ideal for climbing hills. Compact or mid-compact is what tri bikes have for power versus speed over long races.
