The truck wheel seal requirements have changed over the past ten years. Some of the critical requirements for a truck wheel seal in today's environment are: the ability to exclude dust, mud, and water over a wide range of operating conditions; the ability of the elastomeric sealing element to tolerate various aggressive lubricants over a wide range of operating conditions; the ability to provide an adequate OD seal when installed in aluminum housings of various surface finishes; and the ability of the seal to be installed with minimal opportunity for installation damage or improper installation. An improved unitized truck wheel seal was developed to accommodate the above requirements. During the development program, it became obvious that an advanced Nitrile rubber (NBR) formulation was necessary to assist the seal design in accommodating the more demanding performance requirements. The paper will describe the advantages of a new NBR materials developed for use in the improved unitized truck wheel seal.