Many people are willing to spend extra dollars for tires with names like MACHO WILDCATS or TOUGH GUYS embossed in large white letters on the sidewalls, but did you know that the wealth of information that is embossed on those sidewalls in quiet little black letters can be more valuable in the long run And this information is free — if you know how to decode it.
Even if you’re not the inquisitive type, the data in the following sections can help you when you buy and maintain tires. shows you all the different types of codes you can find on the sidewall of a tire.
Tire codes
Until around 1978, tire sizes were indicated by alphanumeric codes, such as D78-14. With the adoption of the metric system, the codes changed drastically, and now modern codes provide more information. Tire dealers are required by law to have leaflets available that explain tire grades and ratings. The leaflets also tell you which metric codes replace the old alphanumeric designations. For example, here’s a breakdown of the information provided by a common “P-metric” tire cod as shown.
areas with extreme conditions, look for these codes on the sidewall. Codes may differ slightly from one tire to another. In addition to the Pmetric code, there are European metric codes, which can be as simple as 155SR13 or as complex as 18 5/70R14 88S, but the data they disclose is pretty much the same.
Speed ratings
Sometimes an additional letter appears between the load index and tire type, such as P21 5/65R15 89H in . The letter H refers to the speed rating, which represents the safest maximum speed for the tire.
It tells you nothing about a tire’s construction, handling, or wearability but rather measures the tire’s ability to dissipate heat so that it can endure the high temperatures that high speeds create.
speed limit. They’re usually good buys because tires with higher speed ratings are more durable. However, if you usually drive at low speeds on local streets and rarely drive on the highway, the extra expense may not be worth it.
DOT identification and registration
The Department of Transportation (DOT) identification number on the sidewall has a wealth of information. Here’s what the letters and numbers of the DOT code mean: DOT indicates that the tire meets or exceeds United States Department of Transportation safety standards.
The next two numbers or letters identify the plant where the tire was made. The next numbers or letters are marketing codes provided by the manufacturer. They serve as a registration number that identifies the tire in case of a recall.
(You can find more information on recalls in the later section “Dealing with Defective Tires.”) The last four numbers are the week and year the tire was produced. For example, 2408 would mean the tire was made during the twentyfourth week of 2008.
Be sure to check this code to see how old the tires on your vehicle really are! In some cases, it can only be found on the inside sidewall, but it’s worth getting down there with a flashlight.
Last word
A 2008 exposé by ABC’s Underground 2 0/20 found that, despite the fact that tires over 6 years old could suffer blowouts that had resulted in a considerable number of fatal accidents, supposedly new tires were for sale at tire dealerships and major chains with codes showing that .
the tires were 12 years old or more! In 2008, NHTSA ruled that this date code had to appear on the outside of the tire where owners could easily check them on their own vehicles. Under federal law, the deal.
