Railway wheel

Railway wheel and tire

Modern railway wheels are usually machined from a single casting, also known as monobloc wheels. Some wheels, however, are made of two parts: the wheel core, and a tyre (CwthE) or tire (NAmE) around the perimeter. Separate tyres have been a component of some rolling stock, their purpose being to provide a replaceable wearing element – an important factor in the steam locomotive era with their costly spoked construction. In modern times the tyre is invariably made from steel, which is stronger than the cast iron of earlier eras. It is typically heated and pressed on to the wheel before it cools and shrinks. Resilient rail wheels have a resilient material, such as rubber, between the wheel and tyre. Failure of this type of wheel was one of the causes leading to the Eschede high-speed train crash.