Have you ever wondered what all those numbers and letters on the side of your vehicle tyres mean? Unfortunately, a meme claiming to explain them has drifted far off course into the misinformation lane.
The meme (screenshot here), posted on the Facebook page of an Australian motorsport and vehicle parts shop with more than 10 million followers, has been shared more than 11,000 times. It shows a close-up of a car tyre’s sidewall with with several numbers and letters highlighted with explanations.
The post’s caption, using US spelling, states: “For those who didn’t have anyone to teach them what the numbers on tires mean.” It goes on to claim the first figure is “tire height in centimeters”, the second “tire lifespan in months”, the third “year the tire was made” and fourth, a “random letter” which “means nothing”.
While the post has a joking tone, transport authorities and motoring groups told AAP FactCheck the explanations are wrong, pointing out the numbers and letters are for varying size and safety aspects of individual tyres.
A spokesperson for Australia’s Department of Transport told AAP FactCheck in an email that “the information is factually incorrect” and encouraged people to “access vehicle information from reliable sources, not viral memes”.
Australia’s NRMA motoring association also said in an email the information in the meme is wrong, as did New Zealand’s Automobile Association (NZAA).
“The numbers are actually tyre ratings,” an NRMA spokesperson said.
The tyre numbers indicate its size, construction type and load index. Tyre manufacturer Bridgestone’s website, along with many other automotive websites (see here and here), break down their meaning.
For example, the meme’s claim the number 45 represents the tyre lifespan in months is incorrect. Instead, that number – the second in the sequence, following the tyre’s width, is the aspect ratio – the tyre height as a percentage of the width.
“The aspect ratio, also known as the tyre profile, relates to the depth of the sidewall,” a spokesperson for NZAA told AAP FactCheck in an email.
The claim the next figure on a tyre – typically preceded in passenger cars by an R (for radial tyre construction) – is the year it was made is also false.
“This (figure) represents the diameter in inches of the wheel on which the tyre is mounted,” NZAA said.
Tyres do have when they were made contained in the DOT code, a smaller series of numbers on the sidewall which typically have the date in a week/year format. For example, 1800 means the tyre was made in the 18th week of the year 2000. Some of the DOT code can be seen on the meme below the larger numbers on the tyre.
The final character is V, which the meme claims is a “random letter means nothing”. It’s actually a code for the maximum speed rating of the tyre, the NRMA says.
Standards for tyre measurements are set by groups including the International Organization for Standardization. Standardisation in vehicles began more than 50 years ago, spearheaded by groups including The European Tyre and Rim Technical Organisation.
The longevity of tyres can differ depending on many factors including how the car is driven, road conditions and vehicle maintenance, such as ensuring the correct tyre pressure is maintained.
Tyre manufacturer Michelin recommends tyres never be used longer than 10 years. The NRMA says “generally speaking, tyres nowadays last for about 40,000km“.
The Verdict
The meme’s claim that a person can determine how long a tyre will last from numbers stamped on its sidewall is false. The large numbers on a car tyre indicate its size and safety factors, and don’t include any indication of expiration. Smaller numbers on most tyres indicate when they were manufactured. How long a tyre lasts depends on many factors including driving conditions and maintenance.
False – The claim is inaccurate.
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