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Thursday, January 8, 2015

DOT Date Code - Why do they make it hard to find and read?

How old are your tires? 

How do you learn the answer?

What is the DOT date code and why is it so hard to find and read?

Answers to these and other important quests can be found right here at

DOT regulations (Law) specify the size of the serial ( 1/4" min) and parts of the content as well as placement (below the midpoint of the sidewall).

The first two characters are a "Plant Code" which as far as I know is standard as I have never seen a variation from the industry code list.

Characters #3 & 4 are not uniform across all tire companies but would be uniform within a tire company and these are a code for the tire size. Sorry but I have never seen a list for all tire size codes for all tire companies. In reality you don't need to know how to "translate" the code as you simply read the size off the tire sidewall.

The next series are optional. These may be used by different tire companies for internal coding. Some companies us no code others may use 1, 2, 3 or 4 characters.

The last four NUMBERS  are the date code, with the first two numbers being the week number starting with 01 and ending at 53 ( The code is changed on Sunday and some years have 52 and some have 53 Sundays. Bet you didn't think of that.) The last two are the last two characters of the year.
Prior to May 2000 the year portion was just a single number but since you should not have tires older than TEN years on your RV you better not have a tire with just  three digits!
The year part changed in 2000 as before that only the last number of the year was used along with another symbol but it was decided in late 1990's that this was too complex so the switch from three to four numbers for the date code.

Since the date code MUST by law, be changed each week this presents some challenges to the manufacture of tires as a person has to do this change. This presents safety issues as reaching the top part of the mold would require a person to climb into the cure press which is HOT (250° to 350°F) and the equipment could accidentally close on the person, so only the bottom side of the mold gets the date portion of the code.

Some car companies have a practice of placing the side of the tire with the full code on the outside but with dual application this means that for RVs the rear tires will have to be different than the front or the date code would be facing the tire that is its mate and very difficult or impossible to read without dismounting the tires from the RV so RV companies do not have this requirement.
This is one reason why whenever buying new tires you should ask for the full DOT serial to be recorded by the dealer on your invoice and that information be stored along with other important papers and information you keep available for future use.

 Here is some information from earlier posts on the DOT serial. If you want to read more just search using the Label list on the left side of this blog.
The DOT Serial

This has important information used in determining the tire age. Other information such as the location of the tire plant that made the tire is part of this code ( first two characters  8X in this example). If there is a recall, this code is used to identify which tires are covered by the recall. NOTE that the last portion, the 4 digit date code, 3908 in this example is only molded on one side of most tires. Every tire sold for use on the highway in the USA must have a full DOT serial including the date code molded on at least one side. This tire was made the 39th week of 2008.

 Do not confuse the fact that the 6E7378 ends with four numbers as there is no 73rd week of the year 2078.

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