Life, as they say, comes at you fast. A few months ago, my wife was driving home from work in our trusty 2007 Ford Explorer when a driver headed in the opposite direction fell asleep at the wheel and crossed into oncoming traffic right in front of her. While she fortunately avoided any permanent injuries, our sturdy SUV was not so lucky.
Suddenly we needed a replacement during a special tumultuous time on the used car market. Wanting to stick to a known quantity, we were able to find a 2008 Explorer that met our expectations. But before we could take our newest acquisition into service, we took it to our mechanic, who pointed out that the eight-year-old all-season tires were well past their expiration date, despite having plenty of tread left.
Seeing that this Explorer is equipped with a true all-wheel drive system, we decided to see what options we had for factory-sized all-terrain tires, and that search led us to the Cooper Discoverer Road+Trail AT. As the successor to the popular Discoverer AT3 4S, the Road+Trail AT is designed to handle rough terrain without sacrificing its on-road driving characteristics. While I was picturing winter trips to the mountains and jaunts through off-road parks, the reality is that this SUV, like most off-road vehicles, will spend most of its time on paved roads.
Not so long ago, opting for a fat all-terrain tire would have been a recipe for excessive road noise, wayward steering and poor handling in everyday use. But as I've learned from testing vehicles like the Ram 1500TRX and the Ring Brothers 1970 Chevy K5 BlazerTire manufacturers have made significant progress on these fronts in recent years, and I was pleased to discover that the Cooper Discoverer Road+Trail AT does not buck this trend. The Explorer's on-road behavior improved even after we fitted the new kit, and there was no discernible increase in road noise compared to the much tamer all-seasons they replaced.
That got me thinking about what's been driving these advances in tire design, so I contacted Cooper Tire, who in turn put me in touch with Jenny Paige. Paige, now director of North American product marketing for Goodyear, Cooper's parent company, oversaw the development of the Discoverer Road+Trail AT in her previous role and was kind enough to chat with her about the project. She said that while a range of different factors have allowed manufacturers like Cooper to make major improvements in tire design in recent years, there are a few developments that have proven to be standout.
“We have made significant progress with the computer modeling we use during the tire development process, and that has allowed us to create more nuanced variations on tire designs before we actually build prototypes. For example, if you look at the tread pattern of the Discoverer Road+Trail, it appears as if it repeats as you walk around the circumference of the tire, but there are actually slight variations in the size and shape of the tread lugs that make up the pattern. And one of the main reasons we do that is because airflow has a huge impact on the road noise a tire generates, especially when it comes to all-terrain tires. By optimizing the shapes and sizes of the profile lugs through computer modeling, we can agitate the air as it moves through those lugs in a way that breaks up turbulence and prevents sound waves from building up.”
She also explained that part of the challenge in developing an all-terrain tire like the Discoverer Road+Trail is that it has to perform well across a wide range of criteria, some of which are diametrically opposed.
“There’s an incredible amount of chemistry that goes into the tread compound of the tire. It’s not just about choosing the raw materials that we have to mix to create the rubber that makes up the tread, it’s also about how we mix them together. That’s not something that consumers can see; it’s kind of the ‘secret sauce’ of tire design. For example, this tire has the Three-Peak Mountain Snowflake symbol, which means it meets the U.S. Tire Manufacturers Association’s requirements for severe winter conditions. To grip in those conditions, the tire compound has to be soft, so that the compound stays pliable as the temperature drops. Typical all-season compounds tend to harden when they get cold, and that makes them very slippery on the road. But since this is an all-terrain tire, the compound also has to be tough and able to withstand rough terrain, rocks and other obstacles. So the trick for our engineers is to find that ‘sweet spot’ with the compound that can perform well in both situations.”
While compound also plays a role in a tire’s behavior in normal weather conditions, Paige told me that sidewall design plays a bigger role in a vehicle’s ability to track straight down the road. But while a stiff sidewall can reduce wayward steering, it can also negatively impact ride quality, so engineers are tasked with striking a balance here, too.
“Remember, there are a lot of different types of rubber in the tire, especially as you get lower into the sidewall, near where it meets the wheel. There are some very stiff compounds in that area that help provide tracking and responsiveness. But we also have to consider ride quality as we try to find that sweet spot. There’s no one tire that can do it all without compromise, so it’s important for us to really understand what the potential customer’s priorities are for the tire we’re developing.”
While computer modeling has become a key part of tire development, real-world testing is still a major part of the process. As Cooper refines a design, prototype versions are produced and evaluated at the company’s test track in San Angelo, Texas, as well as other facilities where extreme conditions can be simulated.
That collected data can send a prototype tire design back to the modeling lab for further adjustments, or to additional laboratory testing at in-house facilities that measure properties such as abrasion resistance and tensile strength. Although the improvements are often subtle, the end result of this process is a better performing, more durable and ultimately safer tire.
