in following prescribed procedures pays off. The following practices are quoted directly from the AAR Wheel
and Axle Manual.
1. Select wheels for application to an axle which will involve a minimum loss of metal in the bore.
2. Apply new wheels whenever possible to second-hand axles with reduced wheel seat diameters.
3. Apply second-hand wheels or worn wheels to new axles or to second-hand axles with wheel seats
nearly standard in diameter.
4. If new wheels must be applied to new axles, the wheel seats should be standard diameter.
5. Second-hand wheels with bores too large for standard wheel seat diameters should be applied to
axles with wheel seats not in excess of 1/8 inch larger than standard.
b. Matching wheels. When matching two wheels for one axle, be sure that they are the same kind, type,
and size. It would not be practical or economical to mount a cast-steel wheel and a wrought-steel wheel on the
same axle because of the difference in their wearing characteristics. The same thing is true with one-wear and
multiple-wear wheels. The size of the mated wheels should be as nearly the same as possible. You certainly
would not match two new wheels with different diameters. In like manner you should select two wheels with
similar amounts of wear left on the treads and flanges and with circumferences of the same size. For example,
if you were using multiple-wear, wrought-steel wheels, you should not pick one wheel with either the flange or
tread worn down near the minimum sizes to mate with another wheel with measurements near the maximum or
new dimensions. Pick two wheels with nearly the same amount of wear left on them.
Remember that the bore sizes must fit the axle seats. If you have matched two wheels and you find one
bore too small for the wheel seat, always re-bore the wheel--do not re-turn the axle wheel seat. You should try
to avoid doing either when you are selecting wheels, but if you cannot find two that match each other and at the
same time fit the axle, you must re-bore the wheel.