Elsewhere in this thread, jcrawfordor explains that hunting oscillation from conical wheels can cause “chatter” at higher speeds which led to BART’s experimentation with cylindrical wheels [1][2]. Others also note that the wheels of high-speed trains are closer to cylinders than cones. [3][4]

[1]: https://news.ycombinator.com/item?id=28350423

[2]: https://news.ycombinator.com/item?id=28350667

[3]: https://news.ycombinator.com/item?id=28350755

[4]: https://news.ycombinator.com/item?id=28352896