Whether you’re purchasing a used car or are just curious about the age of your tires, it’s a useful skill to be able to read the information on a tire sidewall correctly. This ability comes in handy, especially when you’re about to purchase a used car and the seller is claiming the car has brand new tires.
In my experience hunting for cars online over the years, sellers often claim that their car has new tires even if they are two or three years old! This claim is especially important when shopping for high end models such as the M3, M5, or any car with 18” or larger wheels. Buying an M3 on eBay for a good deal will sting a bit when you find out that it immediately needs $1000 worth of new tires. For example, here’s the price of a 19” M3 tire.
One sure red flag is if the seller has no photos of the tire tread surface itself. I’ve seen so many car dealers and flippers juice up the sidewalls of worn tires with tire shine and only photograph the side of the wheel in their listings. If you’re lucky, you’ll still be able to read the date code on the sidewall to determine the age of the tire. Sometimes, making a purchase decision in a time sensitive situation such as an online auction requires using every last bit of available information to make the call.
How to Date a Tire
The sidewall of a tire contains all of the important information you ever wanted to know about that tire. The tire size, tread wear rating, load index, speed rating, date code of week and year of manufacture, traction and temperature ratings, rotation direction, and tire pressure are all listed here.
In the image above, look for the letters and numbers following the DOT marking. The last four digits here are significant; 4500 tells us this tire was manufactured the 45th week of the year 2000. That makes sense, because this is the original spare tire from the trunk of my 2001 E39. Tires this old are definitely not safe to drive on.
Let’s compare that to this new Michelin Pilot Super Sport tire, which I just had mounted on BBS style 42 wheels. Look for the DOT letters, now scroll all the way to the last four digits 0616. This tire was manufactured the 6th week of the year 2016, which makes sense because I just purchased these a few weeks ago. You can also see the tread wear, traction and temperature rating for the tire above.
If I rotate the tire we will find even more information. The maximum load rating and max pressure rating for the tire, which is present in the image above. As a note, this does not indicate the manufacturer’s recommended inflation pressure, nor does it indicate the correct air pressure based on the car the tire is mounted on. Those specs are found on the driver door jam sticker on most BMW’s.
Finally, rotating this tire once more, we can see the size and speed rating. This is a standard size of 235 width, 45 height, and 17 diameter. In the R17 mark, the letter R tells us this is a radial tire. The speed rating on this tire is noted by the 97Y; 97 again is the load index and the speed rating is designated by the letter Y. A tire speed rating of Y is the highest possible and is tested at 186 MPH. Furthermore, since this 97Y is in parenthesis (97Y), that designates that the tire has been tested at speeds above 186 MPH. The perfect tire for Autobahn enthusiasts!