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, directly in front of her. While she was thankfully able to avoid any lasting injuries, our stalwart SUV was not as fortunate.
Suddenly we found ourselves in need of a replacement during a particularly tumultuous time in the used car market. Looking to stick with a known quantity, we managed to find a 2008 Explorer that fit the bill. But before pressing our latest acquisition into service, we brought it to our mechanic, who pointed out that its eight-year-old all-season tires were well past their expiration date despite having plenty of tread left.
Noting that this particular Explorer is equipped with a proper four-wheel drive system, we decided to check out what options we had for all-terrain tires in the factory size, and that search led us to the Cooper Discoverer Road+Trail AT. As the follow-up to the popular Discoverer AT3 4S, the Road+Trail AT is designed to tackle the rough stuff without compromising its on-road manners. While I pictured winter trips to the mountains and jaunts through off-road parks in my mind’s eye, the reality is that, like most all-terrain vehicles, this SUV is going to spend the vast majority of its time on paved roads.
Not so long ago, opting for a chunky all-terrain tire would have been a recipe for excessive road noise, wayward steering, and compromised handling in everyday use. But as I’ve learned from testing vehicles like the Ram 1500 TRX and the Ringbrothers 1970 Chevy K5 Blazer, tire manufacturers have made significant strides on these fronts in recent years, and I was glad to find that the Cooper Discoverer Road+Trail AT doesn’t buck that trend. In fact, the Explorer’s on-road manners actually improved after we bolted the new set on, and there was no detectable increase in road noise in comparison to the much tamer all-seasons that they replaced.
That got me wondering about what has driven this progress in tire design, so I reached out to Cooper Tire, who in turn put me in touch with Jenny Paige. Now the director of North American product marketing for Goodyear–Cooper’s parent company–Paige oversaw the development of the Discoverer Road+Trail AT in her previous role and graciously agreed to talk shop about the project. She said that while a range of different factors have allowed manufacturers like Cooper to make big improvements to tire designs over recent years, there are a few advancements that have proven to be standouts.
“We’ve made significant strides with the computer modeling that we use during the development process of tires, and that has allowed us to make more nuanced variations of tire designs before we actually build any prototypes. For example, if you look at the tread pattern of the Discoverer Road+Trail, it appears to be repeating as you go circumferentially around the tire, but there are actually small variations in the size and shape of the tread lugs that comprise the pattern. And one of the big reasons why we do that is because air flow has a huge impact on the road noise that a tire generates, especially when it comes to all-terrain tires. By optimizing those tread lug shapes and sizes through computer modeling, we can stir up the air as it travels through those lugs in a way that breaks up turbulence and prevents those sound waves from building up.”
She also explained that part of the challenge of developing an all-terrain tire like the Discoverer Road+Trail is that it needs to perform well in a wide range of criteria, some of which are diametrically opposed to one another.
“There’s an incredible amount of chemistry that goes into the tire’s tread compound–it’s not just about picking the raw materials to mix up in order to create that rubber that makes up the tread, it’s also the way that we mix them together. That’s not something that consumers can see; it’s kind of the ‘secret sauce’ in tire design. For example, this tire carries the Three-Peak Mountain Snowflake symbol, which means that it meets the U.S. Tire Manufacturers Association’s requirements for severe winter conditions. In order to get traction in those conditions, the tire compound needs to be soft so that, as the temperature drops, the compound remains supple. Typical all-season compounds tend to harden when they get cold, and they become very slick on the road as a result. But since this is an all-terrain tire, the compound also has to be robust and capable of withstanding uneven 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.”
Although the compound also contributes to a tire’s behavior under normal weather conditions, Paige told me that the design of the sidewall 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 finding a balance here as well.
“Bear in mind that there are numerous different types of rubber inside of the tire–especially as you get lower in the sidewall, near where it meets with the wheel. There are some very stiff compounds in that area which help provide that tracking and responsiveness. But we also have to be mindful of ride quality as we look for that sweet spot. There isn’t one tire that can do everything without compromise, so for us it’s important to have a good understanding of what the potential customer’s priorities are for the tire that we’re developing.”
While computer modeling has become an important component of tire development, real-world testing is still an instrumental part of the process. As Cooper hones in on 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 recreated.
That collected data can send a prototype tire design back to the modeling lab for more tweaks, or on to additional lab testing on proprietary rigs that measure attributes like abrasion resistance and tensile strength. While the improvements are often subtle, the end result of this process is a better-performing, more durable, and ultimately safer tire.
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