Original Equipment Tire Marks: How do they Work? by Evan Williams September 19, 2018September 19, 2018 Share Comments Take a look at those tires on your new car or truck. Look at the markings. No, not the usual ones, like P265/35/19, or the DOT ones. Those are on every tire and just mean the size and age. I mean the other ones. Like the N on a new Porsche. Or the TPC that adorns nearly every new GM vehicle. AO on Audi, F on Ferrari, and even VO on some Volkswagens. Those codes tell you that you’re looking at a manufacturer approved tire. But how does that work? And do you need them? Tires are a huge part of your car or truck. And not just for keeping the wheels off of the ground. Acceleration, braking, handling, steering feel, road noise, fuel economy. They’re all areas where the tire can play an absolutely massive role. Picking the wrong rubber can result in more than a 20 percent decrease in fuel economy, make the car nearly too noisy to drive, ruin stability, and generally make your day miserable behind the wheel. And yes, those are all things we’ve experienced with a bad tire choice. So it’s essential for automakers to ensure that the tire that goes on their car, at least when it leaves the factory, does exactly what the manufacturer wants it to. Enter the OE tire designation. A way for the automaker to let you know that this tire right here is the one that they want on your car. The one that they think will be the best. Sometimes what they think is best and what you think is best are completely different, but that’s because they’re using different criteria than you. If you’ve ever looked at the tire on a new GM vehicle, you’ve probably seen the TPC logo followed by a number. It’s even a cool symbol with the P larger than the other letters. It stands for Tire Performance Criteria with the number a reference to what criteria it meets. GM has a tire and wheel engineering team that sets out exactly what they want a specific car’s tire to do. Then they work with their tire suppliers to make a tire that meets that. They’re understandably secretive about what exactly the criteria are, but they involve noise, traction, hydroplaning, fuel economy, and more tire things we would probably never think of. Porsche does the same. For a tire to get the Porsche N designation, it must pass the company’s tests. That includes top speed on the Autobahn, noise (especially important on massively wide sports car tires), hydroplaning resistance, and we’re going to guess probably handling. A number after the N means that the tire company revised the tire and the new version still passed muster. The company has even recently approved a series of tires for classic models, with recommendations going back as far as cars from 1959. They currently have 2,200 recommended tires available from dealers. Audi says that each tire that wears the AO badge has to pass “around 50 performance criteria tests.” Other automakers use similar methods, but the end result is the same. The tire wears the automaker’s stamp of approval. Literally. That tire is guaranteed to be a good fit for the car it was intended for. With some exotics, though, the involvement is a bit more symbiotic. Much of the tire’s performance, and the performance of the car, are moulded around each other’s specific criteria. But that’s something you might notice on the Nurburgring, not the I-95-ring. So does that mean that you need to buy OE-marked tires? Or that automakers who don’t have marked tires are using bad rubber? Mercedes-Benz MO Continental Well, the tire companies are going to give you a big, emphatic no. Unless they’re the one with the OE stamp. After all, just about every tire sold wears a DOT marking that means it’s at least suitable to be put on a vehicle. And even the tire makers who get an OE stamp often sell the same-name tire in the same size without the marking. And they’re both more widely available and probably cheaper. Porsche N tires, for example, are only available through dealers. And I’ve never seen a TPC-marked tire that wasn’t at a GM store. Does that mean that the Pirelli P Zero in 305/30ZR20 with an N1 is exactly the same as the one that doesn’t have it? And is it different again from the Ferrari-badged F02 tire? They all look the same. But there is more to a tire than the tread. There could be changes to the compound or structure that make it more ideal for what Porsche or Ferrari intended. That said, for a car that isn’t a high-performance track machine, you’ll probably be happy with any high-quality replacement tire. And if your performance targets are different than what the manufacturer targeted, you might be even more happy than you were before. If you want your car to drive exactly like it did when it left the factory, get the OE marked tire. If you’re ok with a bit of a change, consult your friendly neighbourhood tire professional.