In the analysis of rolling-sliding concentrated contacts, such as gears, bearings, and traction drives, the traction characteristics of the lubricant are of prime importance. The elastic shear modulus and limiting shear stress properties of the lubricant dictate the traction/slip characteristics and power loss associated with an EHD contact undergoing slip and/or spin. These properties can be deduced directly from the initial slope, m, and maximum traction coefficient, μ, of an experimental traction curve. In this investigation, correlation equations are presented to predict m and μ for two modern traction fluids based on the regression analysis of 334 separate traction disk machine experiments. The effects of contact pressure, temperature, surface velocity, and ellipticity ratio are examined. Problems in deducing lubricant shear moduli from disk machine tests are discussed.Presented at the 38th Annual Meeting in Houston, Texas, April 24–28, 1983