You may not think of aluminum as being complicated, but there’s an entire array of carefully determined factors that go each and every part of your motorcycle. Yamaha Motor Company prides itself on its aluminum alloys and forging processes, and it credits the care it takes to its parent company’s piano-frame-casting roots.  

How do you improve those processes, if you’re Yamaha? Materials science, baby. Just having a simple recipe to follow and some casting temperature instructions isn’t enough on its own, either. After all, think about how a simple cookie recipe can drastically change in different hands. Aluminum may not be edible, but at least as many variables affect the finished product as the taste and texture of your favorite chocolate-chippers. 

It was just that kind of innovation that led Yamaha to concoct exactly the right combination of ingredients for its spinforged wheel manufacturing process. You’ll find these wheels take pride of place on the 2021 MT-09, where they use a special flow forming process that came from Yamaha Motors Materials Division specialist Kahori Oshima’s research. 

“Just changing a few conditions can completely alter how aluminum reacts, or its ‘personality’ so to speak,” Oshima said in a statement. “It can be really sensitive sometimes, often giving us zero margin for adjustments.” 

“Yamaha has a massive collection of aluminum ‘recipes’ created by our predecessors and this is one of our strengths. We have an ethos here of aluminum being an area of manufacturing that we must never be outclassed in, and I think what lies behind that is the fact that Yamaha has long done casting all on our own. That confidence and pride pushes us,” Oshima added. 

Of course, Yamaha is more than happy to keep its exact recipes and processes to itself as proprietary materials. What they will tell you is that these new spinforged alloy wheels weigh approximately 0.7 kilograms (1.54 pounds) less each than the wheels they previously used. That’s significant unsprung weight savings, right there. Yamaha says that it achieved that weight reduction by getting overall wheel thickness down to just 2 millimeters—where it had previously been 3.5 mm.  

“What we struggled with the most was having no metrics to go on. Without them for evaluation, we can’t figure out where we need to set our target, so it was certainly difficult to develop a material and build an appropriate method of evaluation at the same time,” said Oshima. 

“For example, if it’s strength alone, aluminum can’t beat iron. But on the other hand, aluminum has advantages like its lightness, corrosion resistance, high machinability, and its beauty. Even if our Monozukuri [Japanese cultural business concept of craftsmanship] changes in the future, I’m certain aluminum will remain a material of choice. I believe my role as a materials researcher is to extract and enhance that potential,” Oshima concluded. 

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