49 CFR §215.119

1. (a)A side frame or bolster that—
   1. (1)Is broken; or
   2. (2)Has a crack of 1/4 of an inch or more in the transverse direction on a tension member;
2. (b)A truck equipped with a snubbing device that is ineffective, as evidenced by—
   1. (1)A snubbing friction element that is worn beyond a wear indicator;
   2. (2)A snubber wear plate that is loose, missing (except by design), or worn through;
   3. (3)A broken or missing snubber activating spring; or
   4. (4)Snubber unit that is broken, or in the case of hydraulic units, is broken or leaking clearly formed droplets of oil or other fluid.
3. (c)A side bearing in any of the following conditions:
   1. (1)Part of the side bearing assembly is missing or broken;
   2. (2)The bearings at one end of the car, on both sides, are in contact with the body bolster (except by design);
   3. (3)The bearings at one end of the car have a total clearance from the body bolster of more than 3/4 of an inch; or
   4. (4)At diagonally opposite sides of the car, the bearings have a total clearance from the body bolsters of more than 3/4 of an inch;
4. (d)Truck springs—
   1. (1)That do not maintain travel or load;
   2. (2)That are compressed solid; or
   3. (3)More than one outer spring of which is broken, or missing, in any spring cluster;
5. (e)Interference between the truck bolster and the center plate that prevents proper truck rotations; or
6. (f)Brake beam shelf support worn so excessively that it does not support the brake beam.