Tires are the only part of the vehicle that touches the road, yet consumers hardly pay them any attention, except for when things go wrong. You may have noticed what seems like strange markings or letters on the sides of your tires; but have you ever wondered what they mean? Rather than wait to discover what the symbols and writing on your tires mean, we’re here to divulge the mystery!
The Writing Serves a Purpose While it may seem as if tire manufactures put those letters and numbers there to confuse you, we assure you it’s not the case. Rather, these markings communicate important information to auto repair professionals. Since tire manufacturers can’t attach manuals or letters to the tires themselves, they’ve developed their own language for communicating things like load carrying capacity, the maximum inflation pressures, and max mph; but there’s even more to it. A quick glance at the tire and you may notice a large letter presented on the sidewall of the tire. Depending on the letter, it may communicate different things. For instance, if you see something like “P215”, the “P” lets you know the tire is designed to be used on a passenger car. While something like “LT” lets you know the tire is suitable for use on a light duty truck. The Numbers The numbers will tell you a variety of things depending on where they’re placed. The numbers following the letter will tell you how wide the tire is in millimeters. So, if you have a tire measuring 215 millimeters, your tire is roughly 8 inches in width. Following the letter and numbers is a slash, which separates this key info from the rest. Following the slash is another number, which reveals the difference between the sidewall height, and the width of the tire. In general, the lower numbers are usually reserved for high performance tires. Performance Tires Performance tires differ from everyday tires in their ability to cope with more demanding driving types. They will usually have shorter sidewalls, which will improve cornering ability due to less flexing of the sidewall. “R” Another letter should follow, providing the tire was manufactured in the US. “R” is short for “Radial”. While seemingly insignificant, the letter reveals how the various layers in the tire were arranged during the manufacturing process. Respect to The Past The majority of tires manufactured today are composed of several layers, but there are still some tires composed of one layer. Inferior to our modern tires, these are almost the same type of tire your great grandparents would have used for their vehicles! Times have changed, and for the better. We’re still not done yet! Following this letter is a number which tells us exactly how large the rim diameter is in inches. For those who don’t know, the rim is the metal wheel to which the tire is mounted and usually made of steel or aluminum, or some similar, strong material. Now that we have the size description out of the way, you’ll probably notice even more numbers and letters. More Numbers and Letters The first number you see may vary from between 70 to 130, but this number isn’t just for looks. This number belongs to a complicated indexing system. It’s like a special index for tires. The Tire and Rim Association uses this information to disclose how much pressure the tire can safely handle. It’s safe to assume the larger the number you see, the more weight the tire can safely support. While you would never want to put the tire on a vehicle with an index rating less than the manufacturer recommendations, it’s safe to exceed the displayed number. The Speed Rating The speed rating tells you the safest speed the tires can handle before potential failure occurs. Rather than symbolized as a number, a simple letter gets the message across. At least 10 numbers cover a wide range of speeds, but “S” is the lowest rating you can expect for a tire. These tires are best reserved for speeds at or under 112 mph. Following closely behind “S” is “Q”, which is reserved specifically for snow tires. While designed to perform well in the snow it’s not wise to push these tires past 99 mph. Then again, who wants to race on slick and icy roads? High Speed Tires If you intend to travel at high speeds, then you’ll be pleased to know there are tires that can safely handle speeds in excess of 186 mph. However, the rest of us will probably be perfectly fine with “S” tires. 🙂 The Load Rating As for the load rating (you can usually find this info on the door jamb on the driver’s side), you want to be sure the tires match or exceed the speed rating. The manufacturers set these recommendations on a variety of factors, including heat. Heating Your Tires Up As if driving our vehicles weren’t enough, heat places extra wear and tear on our tires. Too much heat may cause the tires to become weakened over time. The speed rating also correlates to the tires ability to handle it when things get hot, like speeding down the highway at 75mph! Tread Wear Score Next up is the tread wear score, which is displayed as a number, usually in the hundreds. Higher numbers of “scoring” indicates the durability of the tire. Regardless of the number, elemental factors and how we drive our vehicles will be the actual determining factor for this, but since we can’t score tires based on these factors, the numbers will have to do. Traction Rating Traction rating is up next. You’ll see anything from “*”, “A”, “B”, and “C”. “*” is the best, as you’ve probably gathered. Temperature Score Rating The next row of letters is the temperature score rating. Again, you’ll see anything from “A”, “B”, “C”. “A” being the best because of the ability to handle higher temperatures. All Season Tires While not all tires will include “mts”, if your tires do, it means they’re ideal for severe conditions, such as mud and snow. Most all-season tires will feature this lettering. Of course the above details are not the only numbers and letters you might see. Any other following info relates to the tire manufacturer brand, tire pressure recommendations, and DOT serial numbers. Now that you know how to “speak” tires, you’ll be a more informed consumer when it comes time for your next tire purchase!
No doubt there’s been a few times you’ve looked under the hood of your car to discover all the road grime and collected grease. While it’s easier to close the hood and pretend you never saw the mess to begin with, others may want to make the engine bay as clean as possible, whether it’s for personal reasons or they want to make it more appealing to potential buyers.
Over the last three weeks we’ve covered the technical nitty-gritty of how diesel engines work. Now that we’ve completed that short series, here’s something nice to top it all off. This is aa video except from the wonderful Discovery Channel program, “How It’s Made”. Now, you’ll get to see how a diesel engine is made in an Audi automotive factory!