Replacing your cables and housing will keep your bike shifting properly every ride. Housing gets clogged with dirt,mud, and water and keeps your cables from moving freely though the housing. Cables can also fray inside shifters and break in half causing some serious problems. The inner wire of the housing can blow through the ferrules (pictured below) on the end and create an awful creaking noise when you turn you handlebars. It’s good to replace all your cables at least once a year or when you notice a decrease in shifting performance.