Once the foam parts rot, I throw them away and run the entire helmet/straps through a sink full of soapy water. Once rinsed, the helmet's ready to go again. Tossing the foam parts makes the helmet fit better anyway since most are too small for me. I also keep three or four helmets on hand and rotate them so they don't get boring. I'm considering tossing the "visor" parts of those helmets that come with them for safety reasons.