You need at least three, perhaps even four pieces to make it look decent. If you are clever you know how many units a pixel is (1/image_size) and can offset the UV coords properly for fluid non breaking animation.In S44 it's done by having 2 tread pieces for each tread
Alternatively you could say that a certain region on the texture is preserved for all treads and get someone who understands shader languages to write you a pixel shader which moves this region across the UV area