Exactly. The width of the tire alone creates more resistance since the contact patch is so much larger.
Another major factor is the chemical compounds in the rubber. "Eco" tires may sound like their production might have a smaller carbon footprint or something, but they're called that because their rolling resistance is reduced because of the chemicals in the tire. Porsche and BFG engineered a sort of eco tire that still grips like hell for that new hybrid 918 or whatever it's called. I'm curious to see what a set would run for.
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