Originally, all the world’s rubber came from tropical rubber plants. Today, there still is some rubber that comes from plants (it’s called “natural rubber”) but most of it comes from petroleum these days. It’s a simple fact why – it’s cheaper that way.
Funny thing is that even in these days of thousands of raw materials being pulled out of petroleum products, some natural materials are just best for the job. Even when you are making car parts, or specifically tyres. Ready for this?
Yokohama is using the oil from orange peels in two new lines of tyres. The oil comes from industrial citrus farms whose production is primarily destined for the breakfast table. However, after the orange juice is extracted from the oranges, there are lots of orange peels left over. A second harvesting occurs when the oils from these peels is extracted and sold to companies that make household cleaners and fragrances. You’ve undoubtedly seen them at the supermarket or hardware store.
For its tyres, Yokohama utilizes a subset of this orange peel oil that is a very high quality. The primary component of this oil is a compound referred to as Limonene. From a chemists point of view, Limonene is a colorless liquid hydrocarbon classified as a cyclic terpene.
Why orange peel oil? Tyre manufacturers are forever in search of the ultimate rubber compound. What they would like is a compound that has more grip yet exhibits less resistance to rolling. Yokohama claims that its limonene -infused tread, dubbed Super Nano-Power Rubber Compound, does just that. The viscosity of the tread compound in the limonene tyre changes in response to temperature differently than does a tread made with conventional oil. As they explain it, at low speeds, the Yokohama compound exhibits a high viscosity, which contributes to lower rolling resistance. As temperatures increase—during race conditions, as Len Stoler Porsche points out—the limonene viscosity goes down, and that makes the tread compound stickier, which increases grip to a higher level than that of a traditional low-rolling-resistance tyre.
Yokohama won’t reveal how much citrus oil is in the tyres, but a typical tread compound has an oil content of less than 10 percent. And the citrus oil replaces only a small amount of that. In total, however, Yokohama claims that its citrus tyres 80 percent less petroleum than conventional tyres.
The company’s line of “citrus tyres” is currently limited to two models: the Advan ENV-R2 race tyre used in the Yokohama-sponsored Patrón GT3 Challenge and the dB Super E-spec passenger tyre designed for use on hybrids and fuel-efficient compacts.