Prepolymers having active NCO groups are disclosed. The prepolymers are the reaction product of at least one polyisocyanate and a polyhydric component which comprises at least one dimer fatty derivative diol or diamine that is a natural oil based polyol or polyamine which includes the derivative of at least one dimer fatty acid. Polyurethane and polyurea elastomer obtained from the prepolymers are also disclosed. Also disclosed are methods of manufacturing polyurethane or polyurea treaded tires.