Riding with a Gates belt past its due replacement mileage: can it snap or other risks?
The mode of failure I have seen in similar belts used in industrial applications are typically one of two types. In the first scenario the belts show physical damage. The teeth may start to separate or be missing. You may also see cracks on either side of the belt. In the second scenario the belt just snaps. A visual exam will show no wear, cracks or damage. What you will see is the ends of the internal cordage be it Kevlar, Aramid or similar fibers. The second scenario is common enough that belt manufactures generally suggest time or mileage intervals rather than visual inspections. Depending on your model (some are easier to change than others) you could carry a spare belt. As others have commented the belt breaking has some consequences other than inconvenience. Any unexpected component failure can result in loss of control and potential injury.