This report presents the results and findings from a testing program conducted to investigate how wheel temperature may affect wheel surface performance, i.e., the development of rolling contact fatigue (RCF) and wear from November 2019. Under this testing program, a twin disc test machine was used to test two different types of wheel steels (i.e., cast and forged) under a range of temperatures (i.e., ambient to 800 ℉) and slip ratios from 0 to 0.75 percent. This testing program included a total of 32 tests, covering two types of wheel materials, four different temperatures, four slip ratios, and various traction coefficients as a ratio of longitudinal and vertical wheel/rail contact forces.