This study was undertaken to evaluate the likely effect on the wear rate of changing the pinion material in a rack and pinion steering box from carburised SAE-AISI grade 8617 H steel to induction hardened SAE-AISI grade 4140 steel. Accordingly, pin-on-disc unlubricated wear tests were conducted using carburised 8617 H pins and through hardened 4140 pins. The surface hardness of the pins was approximately 60 HRC for both materials. The discs were made of SAE-AISI grade 1040 steel through hardened to a hardness of 45 HRC. The tests were conducted using a load of 2.2 kg and a rotational speed of 60 rpm and also under a load of 28.5 kg and a speed of 99 rpm. The results showed that both the pins and the discs wore more rapidly when the tests were carried out with 4140 pins. The data was evaluated using a wear mode map developed by Lim, Ashby and Brunton. This indicated that the wear mode was mild delamination wear at the lower load and speed but severe oxidational wear for higher load and higher speed.