49 CFR 215.119: Defective freight car truck.

A railroad may not place or continue in service a car, if the car has—

(a) A side frame or bolster that—

(1) Is broken; or

(2) Has a crack of 1/4 of an inch or more in the transverse direction on a tension member;

(b) A truck equipped with a snubbing device that is ineffective, as evidenced by—

(1) A snubbing friction element that is worn beyond a wear indicator;

(2) A snubber wear plate that is loose, missing (except by design), or worn through;

(3) A broken or missing snubber activating spring; or

(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.

(c) A side bearing in any of the following conditions:

(1) Part of the side bearing assembly is missing or broken;

(2) The bearings at one end of the car, on both sides, are in contact with the body bolster (except by design);

(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) 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;

(d) Truck springs—

(1) That do not maintain travel or load;

(2) That are compressed solid; or

(3) More than one outer spring of which is broken, or missing, in any spring cluster;

(e) Interference between the truck bolster and the center plate that prevents proper truck rotations; or

(f) Brake beam shelf support worn so excessively that it does not support the brake beam.