如何將輪胎測試數(shù)據(jù)轉化為非工程專業(yè)人士也能理解的信息？
Discount Tire公司的首席產品與技術官John Baldwin告訴SAE，在Treadwell研究園（Treadwell Research Park）開展的所有工程工作中，有一種神奇的方法可將大量測試數(shù)據(jù)轉化為非工程師也能理解的實用信息。
TRP是Discount Tire的數(shù)據(jù)生成中心，該公司的Treadwell輪胎選購指南背后的算法，使用的正是這里生成的數(shù)據(jù)。該工具采用五星制評分體系，可為輪胎選購者提供個性化且簡明易懂的產品推薦，消費者可在應用程序、網站和線下門店使用該工具。Baldwin 表示，多年來，Discount Tire及其合作伙伴測試了超過2萬只輪胎，涵蓋500到1000種不同類型，包括衍生和升級產品。
然而，測試一款輪胎并得出其滾動阻力系數(shù)為8.2是一回事，向店里的輪胎選購者解釋這一數(shù)據(jù)則是另一回事。
“應該如何告知客戶，一只輪胎不錯但不夠出色？我們的方法是給它打三星，或是三星半的評分，”他說，“這只是借鑒了一些行業(yè)中已有的做法。我們會在后臺對數(shù)據(jù)進行分級。例如，X到Y是五星，Y到Z是四星半。我們的算法使用真實數(shù)據(jù)，希望能讓客戶無需成為輪胎方面的專家就可理解專業(yè)信息。”
據(jù)Baldwin介紹，為了實現(xiàn)這一目標，本身不生產輪胎、只負責銷售的Discount Tire收購了一家輪胎測試機構。這個占地900英畝的測試場地位于德克薩斯州圣安東尼奧附近，之前由Cooper Tire & Rubber公司所有，2021年被固特異輪胎收購。由于固特異在德克薩斯州已經有了一個測試跑道，Discount Tire獲得了收購TRP的機會。
Discount Tire并不參與TRP的日常運營，而是雇傭輪胎測試公司Smithers作為獨立第三方，每年使用該設施約120至150天。此外，一些輪胎OEM在TRP的三個附屬建筑中長租了固定空間。TRP的主樓包含辦公區(qū)和一個配有五個車輛升降機的車庫，而附近的一座維修用樓則存放了輪胎和Matteuzzi胎面打磨機等工具。
在最近的一次媒體活動中，Discount Tire開放了TRP供SAE及其他媒體參觀，讓我們有機會參與類似于Smithers工程師在此開展的一些測試，這意味著我們可以親自體驗Goodyear Assurance Max Life全季輪胎與Michelin Pilot Sport S 夏季輪胎以65英里/小時（約105公里/小時）的速度駛過2英里橢圓彎道時的不同抓地表現(xiàn)。我們還在占地15英畝的濕滑測試場地（帶有1級坡度）上測試了同款電動車和兩輛寶馬M5，并在路錐場地上測試了路特斯Emira Turbo First Edition，最后在越野賽道上測試了Jeep Wrangler Rubicon。當我們停在光滑的混凝土坡道上時，Smithers的TRP跑道系統(tǒng)經理Taylor Floyd向SAE解釋了這項測試為何是評估輪胎膠料的最佳方法。
當我們乘坐的Wrangler停留在30度坡道上時， Floyd解釋道：“在測試三種不同的膠料時，我們會感受到三種不同的‘抓地感’。在進行這類測試時，我們不希望依賴動能，因為動能是一個很難控制的變量。如果盡可能緩慢且穩(wěn)定地爬坡，就能使測試條件保持高度一致。我們可以把不一致的因素移除，并盡可能添加一致的因素。”
光滑混凝土坡道測試可以讓駕駛員評估車輛在某個車輪失去抓地力后，能否重新加油門使車輛繼續(xù)前行，以及是否需要使用差速鎖或其他類似的裝置完成爬坡。Floyd表示，通常認為兩輪驅動可以使車輛爬上坡道，但如果車輛徹底停止，則無法重新獲得前進的動力。而重新啟動爬坡是最關鍵的時刻。在這項測試中，駕駛員需要感受橡膠表面粗糙度與光滑混凝土表面在微小接觸面上的相互作用，也就是說，是抓牢還是打滑。
“每種膠料、每種設計在這些極小的接觸面上彎曲方式都各不相同，”他說。“硅基膠料可能在膠料面的邊緣處含有硅顆粒，這有助于其抓住接觸表面上的微小粗糙點。膠料在輪胎邊緣0.1毫米范圍內的彎曲方式，是最能體現(xiàn)膠料性能之處。嵌在橡膠表面的硅顆粒是否足夠牢固，能提供牽引力，還是會從橡膠表面滑出？膠料在開始撕裂之前能否保持自身結構？這些都是需要測試的問題。”
Baldwin是一位高分子科學家，曾在福特汽車公司任職。他表示，Smithers的測試駕駛員使用SAE J1060標準的10分制主觀評分測試，將駕駛感受量化為數(shù)字。
Baldwin說，“駕駛員完全遵循SAE的規(guī)定，一分（半星）的差距意味著專業(yè)駕駛員可能會注意到區(qū)別，但普通駕駛員不會。差兩分（一星）是普通人可以感受到的變化，而差三分（一星半）則意味著巨大的區(qū)別。例如在濕滑路面上，駕駛員可能會對十個不同指標進行評分。其中，我認為圈速時間屬于客觀指標，而制動性能則是主觀指標，此外還有轉彎、操控、響應、線性、過渡等，測試駕駛員都會進行打分。然后他們會將分數(shù)匯總，得出一個分值（滿分10分），接著我們再將其轉化為五星制。在展示給消費者時，我們可能會將結果進行換算，但背后的實際數(shù)字就是駕駛員的評分。”
Baldwin 表示，早在一個世紀前，汽車行業(yè)就已經開始應用主觀打分的方式了，而 Treadwell的創(chuàng)新解決方案之一，就是使用“參照輪胎”來幫助駕駛員在每次測試時找到基準。參照輪胎通常是一款標準的米其林輪胎，適用于具體場景，但“這并不意味著它們是最好的，它們只是最為一致的。”Baldwin解釋道。這些參照輪胎通常足夠可靠，讓Smithers的駕駛員能夠發(fā)現(xiàn)測試輪胎的問題，而Discount Tire會將這些問題反饋給輪胎制造商。
“我們也會重新審查輪胎，”以確保沒有發(fā)生任何變化。“通常我們覺察到變化，但并不能百分之百保證。因此，當我們發(fā)現(xiàn)一年前的測試結果和現(xiàn)在的數(shù)據(jù)不同時，我們就會聯(lián)系制造商進行詢問，并在Treadwell工具中進行記錄。這么做不是為了記錄歷史，而是對現(xiàn)在的消費者負責。消費者是在今天夠買輪胎，并希望我們幫助他們做出決定。所以我們希望Treadwell的排名反映的是產品的當前狀態(tài)，而不是一年前的表現(xiàn)。”
Treadwell還會測試磨損后的輪胎。在使用配備鑲嵌金剛石刀片的Matteuzzi磨胎機將胎面磨損至4/32英寸后，對其進行類似于歐洲R117 濕地測試協(xié)議的拖車測試。這種測試只需要一條磨損的輪胎，但Baldwin表示，在該測試的開發(fā)階段，工程師需要將車上的輪胎和測試機器之間的數(shù)值關聯(lián)起來，但現(xiàn)在結果已經非?？煽苛??？煽康臄?shù)據(jù)意味著Treadwell本身是值得信賴的，Baldwin表示。
“從技術上講，輪胎不可能總是全新的，”他說。“一旦上路，輪胎的磨損就馬上開始了。因此，輪胎性能存在一個逐漸改變的過程。我們已經讓消費者意識到，應該考慮輪胎在整個生命周期中的性能，而這是以磨損程度來衡量的。”
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.”
一輛特斯拉Model S正在TRC的濕滑地面車輛動力測試區(qū)域進行測試。（Sebastian Blanco）
TRP維修大樓內的亨特對準升降機。（Sebastian Blanco）
Smithers的TRP跑道系統(tǒng)經理Taylor Floyd（Sebastian Blanco）
TRC的濕滑地面車輛動力測試區(qū)域是一個800*800英尺（244*244 米）的賽道，包括一個水深為1.75至2.25毫米（0.07至0.09 英寸）的公路賽道。（Discount Tire）
TRC的越野賽道全長超過4英里（6公里），由硬土、巖石、沙子和礫石鋪成，設有彎道、爬坡和其他障礙。（Discount Tire）
在濕滑條件下測試TRC的30度光滑混凝土斜坡。Discount Tire表示，這一特性非常適合耐久性和主觀牽引力測試。（Discount Tire）