ALT-2 What do the Numbers on a Tire mean
You are shopping for tires, or maybe you just are cleaning those on your car. You notice there are numbers all over the tire. What do these numbers all mean? They must indicate something or they wouldn't be there!
Several of these numbers are very important; particularly if you are in the market for tires and want to ensure you get the best value for your money.
To start you need to verify the age of the tires. It has recently been reported that tires made as long as 10-15 years ago are being sold on the market as "new" tires. While they have never been used, they may not be as "new" as you think.
The composition of a tire changes with age. The older the tire, the less time left in its useful life. Many have lost family members in crashes caused by old tires purchased as new and then failing on a car.
This number is typically located in an oval on the back side of the tire. There is a DOT number. It will either be a three or four digit number, depending on when the tire was made. There may be several characters in front of it, but you just need the numerical numbers.
For example, if you have a tire made before 2000 locate the DOT letters on the tire. Immediately following the DOT may be some alpha characters and then some numbers. It is the numbers at the end of the string you are concerned with. They should be inside an oval. If you see something like 498, that means your tire was made in the 49th week of either 1988 or 1998.
Newer tires made after 2000 have a four-digit code. It would be 5006 indicating it was made in the 50th week of 2006.
Why is this date so important? Several reasons, warranty repairs may be covered on a tire from a specific period after purchase. Without a receipt, they may be covered for a pre-determined period from date of manufacture.
For example, you purchased tires October 31, 2007. The tires you purchased have a date code of 4105 indicating they were made the third week of October two years before. They were already over two years old at the time of purchase.
If you do not have a receipt to prove purchase date, the business you purchased them from will use the tire date to determine warranty.
If they warranty tires for three years from manufacture, you reach that one year after purchasing them. Hang onto your receipt and ensure the age of the tires before purchasing. You can refuse older tires, you are the consumer. Also verify the date when you get your vehicle back to ensure tires weren't switched during the mounting process.
There are many other important numbers as well. There are numbers that tell you how much air pressure to inflate your tires to. Exceeding this pressure may cause abnormal wear and decrease the life of your tires. Keeping your tires below the recommended pressure also can increase wear (but it will appear as different wear than over inflated tires) and can also affect the handing of your car, particularly if have a low tire on the front.
Your tire pressure should be checked in the early morning hours before driving and before the ambient temperature can change the setting.
There is at least one more set of numbers that concern you, however, you typically only get concerned about these when it is time to replace your tires.
You may see numbers strung together like this 235/75R 15.
These numbers are decoded like this.
The number 235 is how wide the tire is across the tread measured from sidewall to sidewall. The measurement is expressed in millimeters. So this tire is 235 millimeters wide.
The number 75 is the ratio of the sidewall of the tire to the tire tread width. The larger this number, the taller your tire will be mounted on the rim.
To find the actual height of the sidewall from tread to rim you need to multiple the width by the height like this. 235x0.75=176.25 mm. This tire has a sidewall height of 176.25 mm.
The last number 15 is the diameter of the rim the tire will be mounted on. This is expressed in inches.
You need to know these numbers when making a new tire purchase to ensure you get a tire that will properly fit your vehicle, not too wide, not too narrow, not for a 13" or 14" rim, and with a sidewall the correct height for your car's designed handling.
However, the most important is the age. Do not buy a tire that is several years old as new. Many will say (particularly tire businesses trying to sell the tires) that age does not matter, but it does. Rubber products have a useful shelf life after which they may still function, but are more susceptible to failure. Protect yourself and be knowledgeable on tire purchased to protect your investment and keep you and your family safe in your car.
