The belt can make noise when forced to run hard against the flanges on the sprockets. This can be due to sprocket misalignment, wheel misalignment, or run out in the drive caused by damaged components. Spraying water on the belt may quiet the drive for a few minutes, but the permanent solution is to correct the alignment or replace the damaged components. Another possible source of noise is a loose front sprocket. Using thread lock on the sprocket bolts alleviates this problem.
In some cases, the noise can occur when riding in dirty conditions, particularly when mountain biking if grit and water temporarily stick to the belt. This noise in no way indicates a problem with your Gates Carbon Drive. In most cases simply hosing off the belt and pulleys after a ride will end the noise. If noise persists, the solution is simple: spray the belt with water, wait for it to dry, and apply a thin coating of dry silicone spray to the tooth side of the belt. Dry silicone dries instantly, helps shed grit, and does not affect the longevity of the belt. We recommend this product.