Damage; U.s. Dot Tire Identification Number - Ford Super Duty Owner's Manual

Damage

Periodically inspect the tire treads and sidewalls for damage (such as
bulges in the tread or sidewalls, cracks in the tread groove and separation
in the tread or sidewall). If damage is observed or suspected, have the tire
inspected by a tire professional. Tires can be damaged during off-road use,
so inspection after off-road use is also recommended.
WARNING: Age
Tires degrade over time depending on many factors such as
weather, storage conditions, and conditions of use (such as load, speed,
inflation pressure) the tires experience throughout their lives.
In general, tires should be replaced after six years regardless of tread
wear. However, heat caused by hot climates or frequent high loading
conditions can accelerate the aging process and may require tires to be
replaced more frequently.
You should replace your spare tire when you replace the road tires or
after six years due to aging even if it has not been used.

U.S. DOT Tire Identification Number

Both U.S. and Canada Federal regulations require tire manufacturers to
place standardized information on the sidewall of all tires. This information
identifies and describes the fundamental characteristics of the tire and also
provides a U.S. DOT Tire Identification Number for safety standard
certification and in case of a recall.
This begins with the letters DOT and indicates that the tire meets all
federal standards. The next two numbers or letters are the plant code
designating where it was manufactured, the next two are the tire size
code and the last four numbers represent the week and year the tire was
built. For example, the numbers 317 mean the 31st week of 1997. After
2000 the numbers go to four digits. For example, 2501 means the 25th
week of 2001. The numbers in between are identification codes used for
traceability. This information is used to contact customers if a tire defect
requires a recall.
2013 F-250/350/450/550 (f23)
Owners Guide gf, 2nd Printing, December 2012
USA (fus)
Wheels and Tires 359