Roadshow Video Reviews
Tech specs on car tiresBuying tires isn't cheap, so know the sidewall specs to shop smart.
-You know, today's cars can go 100,000 miles between tune0-ups. Some of them go 8000 to 20,000 between oil changes. You almost wonder why they have opening hoods on these things anymore. But on thing that keeps wearing out and still cost a bundle? Tires. These really haven't changed in terms of how often you gotta service them. I'm Brian Cooley with a car tech tip: how to read all that data on a car tire and make sure you're buying the right one. Okay. The first thing you usually look at on a car tire is sort of the basic shape and size of it and that's this big line right here: P175/65R-14 on this tire. P means it's for a passenger car, LT is light truck, T is temporary, and ST is for a trailer. Now, 175 is the width of the tire. That's when it's mounted and inflated measured side wall to side wall in millimeters; divide 25.4 to get inches if you care. Notice in a tire that is wide, it tends to have a bigger contact patch, it'll brake better, have more bite for acceleration, and have more grip laterally for cornering. But wider tires are generally bigger, heavier, and have more friction against the road as they ride, so they may reduce your MPG as well. Now, 65 is your aspect ratio after the slash. That's the ratio of height to width. This tire is 65% high as it is wide. The lower that number is, the more you've got one of those cool-looking low, wide tires. Those are also great for sidewall stiffness and, let's face it, great aesthetics these days. But you tend to get a harsher ride and very low profile tires like 45s are very unforgiving of potholes. R means radial. Just about every car tires are radial these days, unless you've got a really old classic car and you put bias plies on it, but that's really rare. 14 is the diameter of wheel it mounts on. That's the size of this hole right here. Now, let's move over here. You'll find this sort of service rating. You got 81S. 81 is a load rating. There's no real easy way to memorize it. You can go look it up anywhere on the Web. The S is your speed rating, the speed at which the tire is designed to run consistently without flying apart. S is only 112 miles per hour sustained. They go way up from there to speeds that only super cars can do. Now, remember that whole Firestone/Ford debacle with tires blowing out and SUVs rolling over? Ever since then, the DOT (Department of Transportation) has been pretty cagey about making sure tires are tracked and recallable, hence this number: DOT and then a bunch of gobbledygook after that. This is your DOT batch and lot number. You're gonna wanna use that later. And the last set of numbers here, these 4 that come after it (like on this car it is 3410), that's your manufacturing date, your freshness date. This tire was made the 34th week of 2010. The older tires (before July or so of 2000) only had a 3-digit code. In that case, it doesn't matter what the code is 'cause they're too old and you should probably replace them. Average shelf life on a tire is generally thought to be 6 to 10 years no matter how much you drive because sun, UV, and ozone cause the rubber to disintegrate just by sitting. Now, some of the old school data is spelled out the most clearly--treadwear, traction, and temperature--in grades. The treadwear is actually an index number based on 100 as an average tire; traction is either AA down to C (this one's an A, so it's pretty good); and temperature is A, B, or C. Again, this is a mid-range tire. It gets a B. Treadwear is not something you really are gonna figure out from that number, though. You're gonna wanna know what this thing is warranted for when you buy it. That's where the rubber hits the road if you will. And in terms of treadwear, there are a couple of ways to measure that. There are wear bars. Do you see these right there? When those are flush with the top of the tread, your tire's done. You're too low. The old Lincoln penny thing still works also. If you can see all of Abe's hair, your tire is worn out. Now., here are a couple of good ones I get a lot of questions on: the colored dots on tires. Here's this yellow one here. When the manufacturer made this tire, the spun it and measure it, and this is actually the light spot. No tire is perfect. It's a little lighter here than anywhere else around the circumference. This can be useful when it's being mounted to a wheel in a way that will cancel that out. This dot here, it's blue on this tire. Sometimes it's red. That's the high spot. No tire is perfectly round. This is where it's a little bit higher around the circumference than anywhere else on the tire. That can also be mounted to the wheel at its low spot and cancel out the irregularities. Good to know if you wanna get your tires mounted really well. Tell the tire guys. They know about this. And by the way, these colored dots and making them on the wheel properly is especially important on a low profile tire because as I mentioned, they're pretty unforgiving in terms of imperfections. That's when you really wanna get these lined up ideally. Now, the thing you'll deal with the most on a tire, or you should, kind of like flossing, is checking your tire pressure. It's like backing up a hard drive. We don't do that either, but you should. Ignore this number. Maximum pressure 44 PSI, that's not the pressure to inflate the tire to. That is set by the manufacturer. You'll find that sticker on your car. And on any car made since about 2007, you've got TPMS--the tire pressure monitoring system--so the car is gonna watch that for you and there'll be some kind of read out or warning on the dash if you're out of spec. Okay. Now, you know how to read a tire like a Kindle, but let me give you one last tip: when you go take all your new found tech knowledge and buy a set of these, don't ignore this little card they give you. You may want to, thinking it's one of those product reg cards that just aims a bunch of junk mail at you. It's not. It's actually run by a clearing house that the tire industry and the government are kind of in cahoots on so they can make sure they can find you if there's a dangerous recall situation on the tires you bought. So right there, you fill in all those numbers that came after DOT that I showed you on the sidewall, and your name and address. By the way, use a durable address. If you move a lot, maybe send it to your parent's address or something so you can be found because tires last for years. The recall maybe way down the road and you'll wanna know about it. Okay. Now you know how to read a tire like a book. Go out there and buy a good set and get them at a good price. I'm Brian Cooley. Thanks for watching.