Use a utility knife to help you cut away the old tread from the bottom of your shoes. The rubber tread should be glued in place. Slice through the glue and pry off the tread piece.
Place the old tread piece over tracing paper. Use a pencil to trace the shape. Add a one inch glue tab on the front and back of the pattern, if they don't already exist.
Cut out the shape you made on the tracing paper and set it on top of a piece of shoe leather, which will be the new bottom of your shoes.
Carve around the pattern using your utility knife. This gives you a template for the new tread. Finish cutting out the tread with a craft knife.
Apply a rubber adhesive all along the edges of the new tread piece, including the glue tabs.
Push the tread in place on the bottoms of your shoes and fold up the glue tabs, so that they're resting against the front and back of the shoe. Keep holding for a few minutes to allow the adhesive time to set.
Wait overnight before you wear the shoes. Put a shoe insole inside each shoe to make the new tread piece more comfortable.