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Boyd Jaynes
Geolander MT launch event
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Yokohama
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Yokohama
Interview by Perry Mack with Fardad Niknam, Director of Segment Development for Yokohama Tires, photos by Yokohama
4WD – Hi Fardad, thanks for taking the time to answer questions about this new tire. Any thoughts to share before we get started?
Fardad Niknam – Thank you for calling. I’ll start by saying that the project started when we first went to consumers to see what they wanted from a new mud terrain tire. We knew we had to be better than the competition. Drivers said they wanted ‘stronger, longer, shorter and quieter.’ A stronger tire that’s more chip- and cut-resistant; a longer lasting tire with reduced tread wear; shorter braking distance on wet surfaces for improved safety and performance; and a quieter tire while driving on-road.
4WD – Sounds great. Let’s start with stronger. Exactly what is GEO SHIELD construction?
Niknam – First, it’s a stronger polyester fiber. We achieved that by increasing the filament core diameter – they are thicker fibers. Secondly, we added two full layers of nylon cap to the belts beneath it. Many manufacturers only use one. Finally, we extended the ply edges further up so the ply protects more of the sidewall.
4WD – What has been added to the tread compound, or how has the manufacturing process been to changed to increase tread life?
Niknam – Most tire manufacturers use a carbon black base compound in this segment. The goal is to get the three compounds to bind together as best as possible. We’ve used smaller carbon black particles, which improve the binding with the other components like natural and synthetic rubbers. We also added silica to the compound. The silica improves the wet braking performance without any compromise in other performance areas . Additionally, we developed a flatter, wider contour concept which improved wear performance.
4WD – Aside from using silica, most tire features involve a performance compromise. You improve one feature only to decrease another. The flat profile gave you longer wear and more traction – what did you lose?
Niknam – Most tires in the segment are rounded and narrower to improve passenger comfort. However, the wider, flatter profile increases the tread life by more evenly distributing the load on the tire. That creates a larger footprint for improved traction and wear. We may have lost some comfort performance with this concept, but we have used other tire elements like belt angel to compensate for some of the losses. These changes result in improved tire wear with a slight compromise on comfort that’s not noticeable to customers.
4WD – You played with the block to void ratio to improve off-road grip while maintaining wet braking performance. How did you determine the tipping point – what measure of traction did you decide was best between off-road and wet stopping distance?
Niknam – As you are aware, larger blocks improve dry braking (more rubber on the road), while larger voids improve wet braking (by the way sand and water behave similarly). Starting with computer simulations, we adjusted the block to void ratio so dry and wet braking were well balanced. Then, we built more flexibility into the tread blocks to help eject mud (and added stone ejectors into the tread base to prevent drilling). As the tire flexes through the rotation, these two design elements help keep the voids clear, improving off-road grip. Then we added jagged siping to improve wet traction. The sipes create suction as the tire rotates, improving wet traction while the jagged sipe construction improves snow traction (like fingers clawing into the snow) without reducing the stiffness of the blocks. The snow performance earned the tire an M+S rating.
4WD – What depth of siping did you use?
Niknam – Most of the siping goes full depth to the tread wear mark. We made sure that customers would get consistent performance throughout the life of the tire.
4WD – What is advanced variable pitch tread? What made you think of trying this to reduce noise?
Niknam – We’ve used variable pitch in some of our other passenger tires so it made sense to use it here to achieve our project goals for this tire. Pitch is how often a block is repeated. We’ve changed the pitch of the blocks from the center of the tire to the shoulder. Using our computer modeling we were able to adjust each pitch by degrees until we found the quietest ride. There is no doubt GEOLANDAR M/T G003 is the quietest tire in M/T segment.
4WD – Thanks again for taking the time to answer our questions.
Niknam – It was a pleasure talking to you.