Riding on coconut shells: Activated carbon inserts made from sawdust and coconut shells could transform your bike
Motorcycle firms have dabbled with the idea of air suspension for decades, but now a British firm have developed a technology that breathes new life into the idea.
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Air suspension, which dispenses with the usual coil springs in the forks or rear shock and relies instead on the compressibility of air, has seen several revivals in the past. In recent years air forks were standard on the 2013-2016 Honda CRF450R and several of its rivals, but the tech has appeared sporadically on bikes for more than a century, going right back to 1909 when Associated Springs Limited (ASL) started building pneumatically-sprung bikes.
In theory, using compressed air as a spring is a great idea. It means you can add or remove pressure from the system via a tyre-style Schrader valve using a simple hand pump, letting you adjust the stiffness and allowing easy compensation for changes in load. But the idea has failed to catch on in a big way for bikes, largely because air springs get exponentially stiffer as the suspension compresses – so settings that work for the initial part of the suspension stroke rapidly become too firm.
To get a gentler progression of stiffness through the suspension’s range of travel, the conventional solution would be to use a larger air chamber, but that is impractical in the confines of a bike.
But Carbon Air’s TruTune inserts can mimic that behaviour without an increase in the physical size of the suspension parts. Made from activated carbon (created from the aforementioned coconut shells and sawdust), they allow air molecules to be ‘stored’ as pressure rises, giving the same effect as a larger air chamber.
Activated carbon contains a huge number of tiny holes called micropores that give it a vast surface area, and it draws air molecules onto this surface as the air pressure increases, effectively storing it as a film on the surface.
Called adsorption (not absorption), this process gives the effect of reducing the amount of air in the shock’s chamber as the pressure rises, creating a gentler increase in stiffness through the suspension’s stroke.
As the fork or shock extends again, the reverse happens – a process called desorption, returning the air from the activated carbon to the chamber as the pressure decreases. The inserts can be used in the positive or negative air chambers to tailor the strength of the effect.
Until recently Carbon Air’s system was under an exclusivity deal with Audi, who have used it on A6 and A7 cars since 2017, but now that has come to an end and opened up the possibility of using the tech on motorcycles.
John Coakley, Chief Technology Officer of Carbon Air, said: "After much testing and talks with manufacturers, we’re ready to bring our TruTune technology to market.
The way the material works is complicated, but applying it to motorbikes is very simple, and the results are transformational. Motorcycle riders will notice a dramatic difference in their ride without losing that ‘soft off the top’ feel.
"Our technology is already proven in the highly demanding automotive industry after being fitted to thousands of current-generation Audi cars. We can’t wait for riders around the world to experience how our activated carbon can seemingly bend the laws of physics."
The firm are now collaborating with motorcycle and suspension companies to bring the technology to the market. And let’s not forget that Audi own Ducati.