Yes, the wheels on the equipment do wear. The standard procedure on the rolling stock is to replace worn wheelsets by axle. ie: pull one axle out of a truck, replace with new axle with new wheels. Locomotive drivers are a different story. We replace the worn tires on an as required basis. Don't forget, the drivers have "Tires" and the drivers are all connected together, so they rotate at the same speed. Individual tires may be changed, but each one must be machined to match the others. Sometimes it is cost effective to replace all the drivers tires at once. We did this on the 41 a few years ago and the 340 is next.