McLaren is 3D printing Titanium wheels and Carbon Performance is printing Aluminum brake calipers, so what about tires? It turns out that they’re at Bridgestone, and they’re making winter driving much safer.
Tire Terminology
Tire technology has advanced significantly over the last century, from strips of smooth rubber to air-filled performance polymers with sipes and regenerative wear patterns. Sipes is the tire industry term for the horizontal and diagonal grooves that are on all tires. The sipes perform multiple functions and affect several characteristics of the tire. Having more sipes improves traction in cold and snowy conditions, but they cause tires to wear more quickly in dry conditions. And the angles, shapes, and patterns of the sipes are customized to affect traction, braking performance, wear, noise, and comfort for the specific application. On top of that, rubber has better traction when it’s warm, so winter tires are made of materials with a lower glass-transition temperature than summer tires because the latter have the hot asphalt to warm them up.
It’s impossible to make a one-size-fits-all tire because of the way that traction, wear, and noise all play tug-a-war against each other. But all-season tires do exist, so how does that work? While those tires do pass the required tests to receive winter ratings and wet braking certifications, they still don’t perform in snow as well as the best winter tires or on dry asphalt as well as the best summer tires. For all-season tires, they find a happy medium with the sipes and the materials, and they work well for a lot of people who live in fairly temperate climates.
Additive Manufacturing: No Compromises
But what if you really could have the best of both worlds? With the help of 3D printing, engineers at Bridgestone are making truly all-season tires. Sipes are put on tires using molds, and traditionally those molds are made by manually attaching strips and chunks of metal to the base tire mold in the desired pattern. The metal pieces are manufactured using conventional machining tools so their geometries are simple. “For a very long time, sipes were basically just a piece of metal in the mold that didn’t have any necessary geometry to it. It just sliced into the treadblock… It’s like a butter knife, it’s a flat blade,” explained Dale Harrigle, chief engineer at Bridgestone. By 3D printing the molds for the sipes, the engineers can include shapes and patterns that could not previously be achieved.
Some of the 3D patterns unlock huge performance gains in traction without the expected loss in performance that comes with wear. “What that 3D profile allows us to do is change the stiffness of the treadblock under braking, under acceleration, so what’s happening is that we can put lots of edges in the tire to enable winter traction. But those edges don’t affect the tire in terms of wear-life or driving or braking traction. It allows us to get the best of both worlds in tire design,” said Harrigle.
It’s not just Bridgestone using AM this way, either. Hankook does it too. And Michelin has been selling tires made with the technology since 2013. Here’s a video where they explain how printing tire molds improves tire performance while reducing production time, material usage, and cost: