The belt should also be cleaned from time to time. Use a damp, lint-free cloth for this purpose. As soon as the belt is clean, no more residue should be visible on the cloth.
IMPORTANT! When removing the belt, be sure to note its orientation and reattach it in the same orientation. It may be helpful to mark the belt on the outside.
A belt loses tension over the years, so it makes sense to replace the belt with a new one after approx. 5 years. We will be happy to check your drive belt and advise you whether a new belt would be appropriate.