Train wheel
type of wheel specially designed for use on rail tracks
A train wheel or rail wheel is a type of wheel specially designed for use on railway tracks. The wheel acts as a rolling component, typically press fitted on to an axle and mounted directly on a railway carriage or locomotive, or indirectly on a bogie (CwthE) or truck (NAmE). The powered wheels under the locomotive are called driving wheels. Wheels are initially cast or forged and then heat-treated to have a specific hardness. New wheels are machined using a lathe to a standardised shape, called a profile. All wheel profiles are regularly checked to ensure proper interaction between the wheel and the rail. Incorrectly profiled wheels and worn wheels can increase rolling resistance, reduce energy efficiency and may even cause a derailment. The International Union of Railways has defined a standard wheel diameter of 920 mm (36 in), although smaller sizes are used in some rapid transit railway systems and on ro-ro carriages.
Wheel geometry and flange
The running surface ("tread" or "rim") of most train wheels is conical, which serves as the primary means of keeping the train aligned centrally on the track while in motion. On curves, the wheelset becomes "self-steering" because of this coning: when one wheel is pushed closer to the adjacent (outer) rail, it presents a bigger circumference to the rail than when centred on the track.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 19, 2026. The linked authority identifier is Q1280719. The Library of Congress control number is sh85020041. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Train wheel” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.