Discount Tire Tests So You Don’t Have To

December 1, 2024

Sebastian Blanco

For all the engineering that takes place at the Treadwell Research Park (TRP), Discount Tire’s chief product and technical officer John Baldwin told SAE Media that there’s actually something akin to magic in the way giga-reams of test data are converted into information non-engineers can usefully understand.

TRP is where Discount Tire generates data used by the algorithms behind its Treadwell tire shopping guide. The consumer-facing Treadwell tool, available in an app, a website and in stores, provides tire shoppers with personalized, simple-to-understand recommendations that are mostly based on a five-star scale. Discount Tire and its partners have tested over 20,000 SKUs, representing 500 to 1000 different types of tires over the years, Baldwin said, including variants and updates. Testing a tire to discover it has an 8.2 rolling resistance coefficient is one thing. The trick is finding a way to explain it to someone standing in a tire shop.

“How do I say that that’s an okay tire but not a great tire? Three. Or three and a half,” he said. “We just latched on to what the world’s already doing. Behind the scenes, we’ll have it, in that case, bucketed. X to Y is a five-star, Y to Z is four and a half, those kind of things. The algorithm actually does take the real data. The expectation is our customers are not going to become experts on tires.”

To do that, Discount Tire - which does not manufacture tires, it just sells them - bought itself a tire testing facility. The 900-acre site near San Antonio, Texas, was previously owned by Cooper Tire & Rubber Company before it was purchased by Goodyear in 2021. Since the company already has a test track in Texas, Goodyear offered Discount Tire the opportunity to buy the TRP, Baldwin said.

Discount Tire is not involved in TRP's day-to-day operations. Instead, tire testing company Smithers acts as an independent third party that uses the facility around 120-150 days a year. Some tire OEMs – Discount Tire would not name them – rent permanent space at TRP in the three outbuildings. The main building houses offices and a garage with five vehicle lifts, while a nearby maintenance building holds stacks of tires and a Matteuzzi tire buffer, among other tools.

Test for yourself

During a recent media day, Discount Tire opened TRP to SAE Media and other outlets. We were able to participate in tests similar to what the Smithers engineers do there. That meant feeling the way Goodyear Assurance Max Life All-seasons pulled differently from Michelin Pilot Sport S summer tires around the curve of the 2-mile oval at 65 mph (105 km/h). We tested those same EVs and two BMW M5s on the 15-acre wet track with a one-degree slope and a Lotus Emira Turbo First Edition through some cones before running a Jeep Wrangler Rubicon through the off-road course. While we were stopped on the polished concrete hill, Smithers’ TRP track systems manager, Taylor Floyd, told SAE Media why this is a great way to test tire compounds.

“If you’re testing three different compounds, you’re gonna have three different ‘feels’ of how easy it is,” he said as we sat in the Wrangler angled at 30 degrees. “When you’re doing this type of testing, you don’t want the momentum because that’s already a variable that is really hard to control. If you go up there as slowly and as steadily as possible, you can be the most consistent. You can take something inconsistent and try to add whatever consistency is possible.”

The polished concrete hill test is where drivers evaluate how much throttle they can add before the vehicle starts up again if the vehicle loses traction at any corner, and if the driver needs to engage a differential lock or something similar to complete the climb. Floyd said the usual expectation is that 2WD will get the vehicle up the slope but will not be able to restart forward momentum once it comes to a complete stop. Restarting up the hill is the moment of truth. What the drivers are trying to feel with this test, he said, is how well the roughnesses of the rubber surface and the polished concrete surface play together at the tiniest of scales to either stick or slip.

“Each compound, each design is going to have a different way it flexes at that really small interaction face,” he said. “A silica-based compound may have silica pieces at the edge of the compound face, and that helps grab onto the small roughness of the surface itself. How the compound flexes in that 10th-of-a-millimeter range at the edge of the tire, that’s where the compound is having the most effect. Is the little piece of silica stuck in the rubber surface well enough to provide traction, or is it going to slip out? How is the compound holding on to itself before it starts to tear apart?”

Subjective/objective

Baldwin, a polymer scientist who previously worked at Ford, said the Smithers test drivers use the SAE J1060 10-point subjective rating test to turn feelings into numbers.

“The drivers all follow the SAE rules for that,” he said. “A difference of one means a professional driver may notice the difference, but your average driver wouldn’t. Two is normal people, and three is a huge difference, which translates into half, one and one and a half stars. Let’s say out on the wet, they might have ten categories that they’re rating. There’s the lap time, which I consider objective, but then there’s breaking, which is subjective out there, cornering, steering, response, linearity, transition, all of those things that then they’re putting ratings on. Then they add it up, and they come up with [a score] out of 10 points, and we turn that into the five stars. We might be stylizing it when we show it, but the actual number behind the scenes is whatever the driver comes up with. That’s the number we use.”

Baldwin said the automotive industry has been dealing with these sorts of subjective reviews for a century, and one of Treadwell’s solutions is the use of control tires to help drivers find the baseline each time. These are usually represented by a standard Michelin tire for the application at hand, but “it doesn’t mean they’re the best,” Baldwin said; they’re just the most consistent. These control tires are usually so reliable that Smithers’ drivers have been able to identify manufacturing problems that Discount Tire has then reported back to the tire OEM.

“We re-audit tires too,” he said, to make sure nothing’s changed. “Usually, we would know, but not always. So when we get different numbers than we did a year ago, we would call the manufacturer and go, ‘Hey, what’s up?’ What will happen is we’ll report that in Treadwell. This isn’t about history. This is about today. Someone’s buying tires today. So we want to help them make their decision. We want Treadwell to rank with what the product is today, not what it was a year ago.”

Treadwell also tests worn tires, using that Matteuzzi tire buffer with diamond-encrusted blades and other surfaces to wear them down to 4/32nds before sending them on a trailer test that’s similar to the European R117 wet testing protocol. This test requires only one buffed tire, but Baldwin said that when the engineers were developing the test, they had to correlate between the on-vehicle tires and the machine, but the results are now solid. Reliable data means Treadwell is itself reliable, Baldwin said.

“If you think about it, technically, nobody drives on new tires,” he said. “They’re wearing right away. So there’s this whole gradient of change. We’ve driven an awareness that we should be thinking about the performance of your tire through its life and its life as being defined as wear.”

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