[Spridgets] DOT - Tire Identification Number

Guy R Day grday at btinternet.com
Wed Sep 29 02:52:15 MDT 2010

This is a good question.  Wikipedia do a very good article on tyres for 
everything but tyre dating but CarBibles on 
http://www.carbibles.com/tyre_bible.html have a reasonable section.

You need a little background for tyre dating as it is a real mix for older 
tyres and did not feature highly on many manufacturers needs.  I understand 
ETRA was the first Association to demand a proper system.  Even so this was 
only around 10-15 yrs or so ago.  Individual tyre manufacturers had their 
own systems that ranged from a pattern of pimples to number codes similar to 
today's.  The number code you see will either be a 3 or 4 figure number with 
an agreed standard between the various tyre Manufacturer Associations as a 4 
digit number.  The first 2 are the month and the second 2 are the year.  If 
it is a 3 figure number this will probably mean it was manufactured before 
2000 but the first 2 are the month and the last the year.  This left a 10 
year cycle for numbering and tyres that are 10 ands 20 years old do 
re-appear.   Don't forget some manufacturers used 4 fig numbers before then.

A 3 figure number on a tyre sidewall means it is now over 10 years old and 
needs rejecting.  Or, it means the tyre wasn't made to a Tyre Assoc standard 
and I wouldn't use it.  It is generally accepted that for car tyres 6 years 
is the upper age limit although various other numbers have emerged.  The way 
tyres are kept before use has a great deal to do with their longevity.  You 
will hear of tyre wear and use long after the 6 year figure and some are 
lucky, others are not.  Tyres need to be used to last, the chemical 
structure and molecular bonding within the tyre will embrittle if it isn't 
used and there is the possibility of an instantaneous decompression - a 
technical term known as a blow-out!

As each manufacturer did their own thing you may get the date code followed 
by a square (1980-1999) or a triangle (1990-1999) or an oval or circle or 
you may find the date number is enclosed within those shapes.  Or the 10 
year marker (or even the date number) may not be there at all.

The question was 'how do I tell the year of the dot number?'  The answer is 
that all of the numbers given have a 3 figure number and so should be over 
10 years old.

Guy R Day

----- Original Message ----- 
To: "Midget/Sprite" ; "Sprite" ; "spridgets"
Sent: Tuesday, September 28, 2010 6:45 PM
Subject: [Spridgets] DOT - Tire Identification Number

> How do you tell if these dot numbers are 2009 or 1999 - 2010 or 2000?
> 360,109,109,109
> http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=11
> Vigil
> _______________________________________________

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