49 C.F.R. § 230.109 – Tender trucks.

(a) Tender truck frames. A tender truck frame shall not be broken, or have a crack in a stress area that affects its structural integrity. Tender truck center plates shall be securely fastened, maintained in a safe and suitable condition for service, and provided with a center pin properly secured. The male center plate must extend into the female center plate at least 3/4 inch. Shims may be used between truck center plates.
(b) Tender truck bolsters. Truck bolsters shall be maintained approximately level.
(c) Condemning defects for springs or spring rigging. Springs or spring rigging with any of the following defects shall be taken out of service immediately and renewed or properly repaired:
1. (1) An elliptical spring with its top (long) leaf or any other five leaves in the entire spring pack broken;
2. (2) A broken coil spring or saddle;
3. (3) A coil spring that is fully compressed;
4. (4) A broken or cracked equalizer, hanger, bolt, gib or pin;
5. (5) A broken coil spring saddle; and
6. (6) A semi-elliptical spring with a top (long) leaf broken or two leaves in the top half broken, or any three leaves in the entire spring broken.
(d) Tender securing arrangement. Where equipped, tender devices and/or securing arrangements intended to prevent the truck and tender body from separating in case of derailment shall be maintained in a safe and suitable condition for service.
(e) Side bearings and truck centering devices. Where equipped, side bearings and truck centering devices shall be maintained in a safe and suitable condition for service.
(f) Friction side bearings. Friction side bearings shall not be run in contact, and shall not be considered to be in contact if there is clearance between them on either side when measured on tangent level track.
(g) Side bearings. All rear trucks shall be equipped with side bearings. When the spread of side bearings is 50 inches, their maximum clearance shall be 3/8 inch on each side for rear trucks and 3/4 inch on each side for front trucks, where used. When the spread of the side bearings is increased, the maximum clearance shall be increased proportionately.