Inexplicable wheel grime?

[Brakie]

Could your wheels be developing an electrostatic charge that attracts the grime?
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That's exactly why I changed wheels on that use Atlas S4..The plating was worn off and I nip the potential problem in the bud.I would exam the wheels using a magnifying visor.

Thanks to my experiences over the years I'm the last to jump on the dirty track as the root of all locomotive problems.That doesn't apply to sound equipped locomotives since a fly spic of dirt will cause issues-maybe not quite that bad.