DOT code (tire identification number)

How to read it

Under 49 CFR 574.5, a new tire’s TIN has 13 symbols in three groups: a three-symbol plant code that NHTSA assigns to the manufacturer, a six-symbol manufacturer’s code, and a four-digit date code giving the week and year of manufacture. The manufacturer’s code may describe significant characteristics of the tire or identify the brand name owner. The same section says the DOT symbol is a certification that the tire conforms to an applicable Federal Motor Vehicle Safety Standard, and that it must not appear on tires no standard applies to. USTMA calls the TIN the tire’s serial number. It exists for recalls: NHTSA’s 1999 rule says the identification requirements are there to let purchasers be told if their tires are found defective or noncompliant.

Also searched as: DOT number, TIN, tire identification number.

Older codes with a two-symbol plant code

Makers first given a two-symbol plant code could keep using it until April 13, 2025, with an older layout of four groups: the plant code, a tire size code of no more than two symbols, an optional group of up to four symbols (which identifies the brand name owner when there is one), and the date code. That is why guides count the code differently. Hankook says eight to thirteen letters and numbers follow DOT; Toyo describes the first two symbols as the plant code.

Retreaded tires

A retreader’s TIN has seven symbols: its plant code and the date code, with no manufacturer’s code. A separate letter R marks the tire as retreaded, and 574.5 says the R is not part of the TIN.

Which side it is on

Since September 1, 2009, FMVSS 139 has required the full TIN on the tire’s intended outboard sidewall. The other sidewall carries either the full TIN or a partial one without the date code; Toyo says the partial number shows the manufacturer, plant and size but not the week and year. NHTSA’s tire page notes that the TIN may not be on both sides.

Letters a TIN doesn’t use

574.5 lists the only symbols allowed in a TIN: the digits 0 to 9 and the letters A, B, C, D, E, F, H, J, K, L, M, N, P, R, T, U, V, W, X and Y. G, I, O, Q, S and Z are not on the list, so a round character in a TIN is a zero.

DOT code or E-mark?

The regulation’s word for the DOT symbol is certification, and 574.5 has the manufacturer or retreader place it. Pirelli’s UK guide reads DOT as meaning that the government agency has approved the tyre. The E-mark is an approval: the Australian Tyre Industry Council describes it as approval by a national authority, with a number for the country that granted it.

In Canada

Canada’s Motor Vehicle Tire Safety Regulations set out a TIN of the same shape (a manufacturer code of two or three symbols approved by the Minister or by NHTSA, a two-symbol size code and a four-digit date code) and let makers use the US layout instead. Canada’s own mark is the national safety mark, moulded into one sidewall.