Figure 4-7. Subsurface defect found on turning
(1) Road dirt and oil mixture on front face of
plate and underside of rim, cindered (burnt) to a hard
consistency or burnt away.
(2) A deep "blue" color on the flange, tread,
or front face of rim, any or all of these conditions.
(3) A uniform pattern of "reddish brown" color
covering back face of rim and extending down into plate.
This same coloring may also be present on front face of
rim and plate.
Figure 4-8. Shelled tread.