Re: Technical Wheel Question

From the Feds:
PART 230--STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS
Subpart C--Steam Locomotives and Tenders
Sec. 230.112 Wheels and tires.
(b) Gage. Wheels used on standard gage track will be out of gage if
the inside gage of flanges, measured on base line is less than 53 inches
or more than 53-3/8 inches. Wheels used on less than standard gage
track will be out of gage if the inside gage of flanges, measured on
base line, is less than the relevant track gage less 3-1/2 inches or
more than the relevant track gage less 3-1/8 inches.
(c) Flange distance variance. The distance back to back of flanges
of wheels mounted on the same axle shall not vary more than 1/4 inch.