The meaning of dot tire numbers

Written by sean russell
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The meaning of dot tire numbers
All tires made in the U.S. must include Department of Transportation identification numbers. (tire image by Orlando Florin Rosu from Fotolia.com)

Under federal law, each tire manufactured in the United States must have standardised information stamped onto the sidewall. This information is pertinent to all drivers, as it indicates tire specifications, ratings and grades important to performance and safety. Department of Transportation tire identification numbers are also federally required and provide further tire information.

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Significance

Multiple tiers of safety measures are required for each tire sold within the United States to lessen the chance of failure, accidents and unsafe driving situations. These measures are manifested in manufacturer specifications, Uniform Tire Quality Grading System standards and a U.S. Department of Transportation identification number. Tires without a DOT identification number are illegal and could be unsafe. Reducing vehicle breakdown and accidents caused by tire failure starts by checking to see if your tires are DOT-rated.

Function

A tire stamped with a DOT identification number means it has met all federal standards legally required for use on American roads. Along with signifying a standard of safety, a DOT identification number represents the date and place a tire was manufactured.

Identification

DOT tire numbers are stamped onto each tire sidewall. They are smaller than the tire brand name and tire width, aspect ratio, speed rating, load rating, wheel diameter and construction type, which could look like 240/35R19 87Y. After the "DOT" stamp, the next two characters signify a manufacturing plant code telling where the tire came from. The next set of digits, not counting the last four, indicate manufacturer-specific marketing codes like a tracking number used in the event of a tire recall. The final four digits indicate the date of production. For example, in DOT U4KL8JR1208, the "1208" means the tire was produced during the 12th week of 2008.

Expert Insight

Buying a new tire doesn't necessarily mean it was recently manufactured. Tires can sit for extended periods of time before being sold. When buying new tires online or from a local distributor, it is important to read the last four DOT identification digits to determine the tyre's true age.

Warnings

According to Car and Driver, the majority of tire manufacturers recommend keeping tires no longer than 10 years after their manufacture date, no matter what the tread or tire health resembles. Audi, Ford, BMW and Volkswagen recommend changing tires before they reach six years post-production. For those who have a vehicle with old tires, it is important from a safety standpoint to double-check the DOT tire numbers to calculate if it is time to replace them.

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