A model is developed to describe the effects of adapter crown wear on the misalignment of a railroad tapered-roller bearing. Wear of the crowned surface results in a flat on top of the adapter. This flat, in contact with the wear plate, is shown to have the capacity to transmit a moment between the bearing and the side-frame of the truck. The magnitude of the moment transmitted is dependent on the length of the flat. These analytical results are coupled with model results from a bearing manufacturer, which give the relationship between bearing misalignment, and thus transmitted moment, and reduction in fatigue life of the bearing. The analysis indicates that a slightly worn adapter has no appreciable effect on the rated fatigue life of the bearing, but once a threshold level in adapter crown wear is reached, the bearing fatigue life will begin to decrease. Large amounts of adapter crown wear will result in significant bearing misalignment and a corresponding reduction in the fatigue life of the bearing.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999