As BikeRadar reported back in February 2015, graphene – a close sibling of graphite, that black stuff everyone will recognise as the middle bit of a pencil – has been causing a bit of a stir in the bike world.
It's not just bikes though – graphene has become a big tech story globally, with the promises of this 'wonder material' making advances as far-reaching as aerospace, environmental cleanup applications and electronics.
Italian tire master Vittoria recently invited us to see what it's got in store with a visit to its graphene technical partner Directa Plus on the shores of Lake Como in northern Italy. Click through the gallery above for an in-depth look at what goes on in the graphene factory – and how its properties benefit bike wheels and tyres.
What the heck is graphene again?
Graphene is refined graphite. The raw mined material is put into an expansion ‘system’ where it's hit with plasma with a heat range between 6-10,000C – that’s about the same as the surface of the sun!
This leads to massive expansion of the raw material, so it goes from a solid lump into what looks like black cotton candy after this process. The graphene has an enormous surface area, with 1g equating to around 2630 square metres.
This model shows the uniform structure of pristine graphene
The graphene is then refined further into either pellets as an additive to other materials, a liquid form or the cotton-like state depending on the final application. It is strong, light and conducts electricity and heat.
Using graphene can have environmental benefits, according to Directa Plus. In its pure state it’s very hydrophobic, so it’s not a danger to watercourses if it ends up in landfill. In fact, the company is developing graphene-based solutions to pollution, because 1g of graphene can absorb 90g of hydrocarbons.
Directa Plus refines graphene into many different end products
One of the most interesting products Directa Plus has developed along these lines is called ‘Grafysorber’, used in large sausage-shaped ‘boom barriers' capable of not only containing sea-based oil spills but also absorbing oil at a rate of 80/90g per minute – two to three times better than current polypropylene solutions, which are themselves environmentally nasty. Impressively these booms can then have the oil extracted from them and be reused again and again.
But for bikes?
Vittoria started out putting graphene in carbon rims, where it claims, the material's unique qualities are put to good use. First of all, graphene's strength is 200 times that of steel, yet it has half the density of aluminum – obviously strong starting points for making something stronger and lighter.
The ‘pristine’ graphene material Vittoria adds to the resin in its carbon rims has another significant effect: it makes the resin a much better thermoconductor. While carbon is a good thermoconductor, standard resins are not. This is why braking for extended periods on a carbon brake surface can lead to significant buildups of heat, which can lead to pressure blow-outs on tyres and – in the worst case scenario – going beyond the Tg limit (AKA the 'glass transition') and failing catastrophically.
Vittoria’s competitors have used various methods to reduce heat buildup. The addition of basalt, resin reduction in the brake surface, surface treatments, special pads and even copper filaments have been tried. Vittoria claims, however, that because its proprietary resin is used throughout its rims they can dissipate heat faster and more effectively than the rest.
Vittoria's Quarano wheels and Corsa tyres now use graphene in their composition
The other beneficial effect of graphene is its elasticity, which is six times that of steel. According to Vittoria, this makes the rims far more resilient to impacts, meaning they're capable of returning to their original shape after a big strike. This is something mountain bike rims can obviously also benefit from.
Some more numbers?
For those who prefer the last bit stats, Vittoria tested two sets of identical wheels, one with the graphene fairy-dust treatment and one using standard carbon.
It found the graphene wheels had 10 percent better thermal dissipation, 15 percent weight reduction, 26 percent increase in material strength, 18 percent increase in impact strength, 20 percent increase in spoke hole strength, 20 percent more flexibility and, finally, a 50 percent increase in lateral stiffness. Crikey.
Breaking fresh tracks
It's tyres where the interesting stuff seems to be happening though. Vittoria has named its Graphene+ tyre range ITS, for ‘intelligent tyre system’.
Despite using hi-tech materials like graphene, Vittoria's road tyres still use core-spun cotton casings and they are still made by hand
Vittoria says the graphene-infused compounds used in its tyres can actually change depending on how the tire is loaded. For the road tire that means when rolling straight the rubber is at its hardest, but if you load it in another direction, braking, accelerating or leaning into a corner the compound softens offering significantly more grip.
Independent testing at Finland’s Wheel Energy showed a 32-second advantage in the new graphene-infused Corsa tire over the previous generation at 50kph for 50km – or a 10w saving per minute of effort. If these claims are backed up on the road then this represents a serious advantage. The new Corsa Speed, meanwhile, is tubeless ready and weighs just 205g for a 23mm model – impressively light for a tubeless road tyre.
How a tyre changes its softness is a tricky one to explain. Vittoria’s Christian Liederman told us that the graphene platelets in the rubber compound are uniform in their composition, running in parallel lines, and because of their extreme elasticity they stretch and spread when deforming in a very uniform manner, it increases the contact patch when you need it most and gives more grip.
The new Corsa G+ after 6,000km of testing – while worn, there's little sign of cuts, cracks or delamination
The other benefits of the material are longevity and puncture resistance. We looked at a Corsa that had been ridden for 6,000km, and the wear looked incredibly regular – we couldn’t see any cuts or tears just a very evenly worn surface. Vittoria claims it's three times harder wearing than its previous lightweight handmade cotton-cased open tubulars.
The puncture resistance looks truly impressive. We watched the new Corsas being ridden over a series of nails at a medium speed, and the instant sealing post-penetrating spiking is the fastest we’ve seen on any road tubeless tyres.
Again, Liederman puts this down to the uniform nature of the graphene's structure, which bonds at a molecular level with the rubber compound. This means, he says, that as soon as it's disrupted it wants to spring back to its original shape, sealing any puncture tightly and enabling the sealant to do its work.
For mountain bikes Vittoria has completely redesigned its tire range. The composition includes four distinct rubber compounds; by infusing with Graphene+, Vittoria claims it's been able to significantly decrease the weight of its off-road tyres while increasing the knob strength.
Under an electron microscope you can see the much more uniform structure of a graphene-infused tire
Using multiple compounds within the knobs themselves mean they can be softer at the peaks and stiffer at the base, or vice versa depending on position. Vittoria says the unique way in which the G+ rubber reacts to deformation increases grip in critical situations.
At the moment Graphene+ is only in a handful of Vittoria’s tyres. But the brand claims that within two or three years the material will be in all of its range, from entry- to pro-level.
Vittoria also has a tubeless road wheel based on the current Quarano range arriving in January (though it didn’t have one to show us). It's looking as well into the possibility of graphene/carbon disc brake rotors, bicycle frames (in collaboration with undisclosed partners) and – interestingly – graphene-infused yarns for cycling clothing.
Vittoria definitely wants to shout about this whole graphene thing
In the latter case, Vittoria believes the high elasticity yet incredible strength of graphene can deliver super lightweight form-fitting garments that are also highly abrasion resistant. (Think a step on from Scott’s Pro Tec, or Giant Alpecin’s Dyneema shorts as used in this year's Tour de France.)
Pricing on the new tyres is $125 / £78 for the Corsa tubular and $84 / £53 for the Corsa clincher. The new Corsa Speed is £85 / $135 in tubular and £60 / $90 in tubeless ready.
We’ve got wheels and tyres from the new Graphene+ range incoming for test, so we’ll report back soon to see if they live up to the not inconsiderable hype.