Exclusive: Sam Hill's Secret Weapon

When Schwalbe introduced its tire-inside-a-tire Procore system this year, most people believed that it was developed primarily to prevent pinch flats from scuttling a downhiller's race run. Surely, pinch-flat protection was one of the motivations for Procore, but the inception of the design actually came about as a means to solve a far more important problem - one that bicycle suspension designers have been wrestling with for fifteen years. Procore tire technology was the brainchild of two German think tanks: the engineers at Schwalbe, and the people at Syntace. The information about this synergistic relationship was revealed at the Dornier Aviation Museum across the Zeppelin port from the Eurobike Expo in Friedrichshafen, where Schwalbe officially launched its 2015 range.



At the museum, I had the opportunity to speak with Syntace founder Jo Klieber, one of the industry's most progressive and creative thinkers, and the man who began the development process which ultimately led to the Procore system. Kleiber said that he was experimenting with the rolling efficiency of the three wheel diameters versus the effectiveness of large-volume tires. Klieber rented an expensive high-speed camera so he could watch how the tires deflected and the suspension reacted to bumps of various shapes and sizes in slow motion. Klieber said that while viewing the slo-mo recordings, he was surprised to discover that the tires would deflect almost to the rim - sometimes actually contacting the rim flanges – before the rear suspension or fork would begin to move.

Using telemetry to track the way that the tire and suspension interacted after an impact revealed that the spring rate of the tire was very linear and that it ramped up too gradually to overcome the suspension's static friction. When the suspension did begin to move, the hand-off between the spring rate of the tire and that of the suspension created a distinct spike in the compression rate at the very moment when the suspension should have been progressing smoothly through its stroke. The result was a lack of compliance for soaking up small to medium-sized bumps. Up until now, suspension tuners have wrestled with compromises to eliminate the spike. The most common solution has been to over-inflate the tire, which stiffens its overall spring rate and thus activates the suspension at an earlier moment - but that fix also reduces traction and small-bump sensitivity.



Klieber reasoned that if he added a second, highly pressurized casing inside the tire, the spring rate of the tire would ramp up faster when the two began to compress in unison and thus would activate the suspension in a more seamless and gradual manner. If successful, the tire-inside-of-a-tire system would allow the rider to use lower pressures and at the same time, force the suspension and tire to react as a single unit to small bumps. Klieber predicted that both actions would dramatically enhance traction, along with the potential benefit of reducing pinch flats. Syntace, however, could not move forward on the project without securing a partner willing to produce the inner tire, which was a non-standard diameter. They contacted their friends at Schwalbe tires, who were excited about the project, but unable to respond with prototypes at that time. Klieber and company would have to wait.

Finally, Syntace engineer Oliver Zuther took matters, literally into his own hands and crafted some tubular tires in his basement that could be glued into the wells of Syntace's rims. Klieber says that testing immediately showed that the hybrid wheels performed as they imagined, and armed with the results, Syntace again approached Schwalbe for assistance to get the concept to market. This time, Schwalbe was already working on a similar concept that was intended to eliminate pinch flats for gravity racers. The two companies decided to join forces and produce one design that could address Klieber's vision of mating the tire's performance with the bike's suspension and Schwalbe's desire to end the dreaded pinch flats that so often sideline gravity racers.



In the end, Procore delivered more than expected. Schwalbe's insistence that the inner tire be a clincher type instead of a tubuler had the effect of pinning the beads of the tubeless outer tire to the rim's flanges, so if the main tire flatted, it would remain on the rim and still be rideable for the entire race run. Pinch flats were almost completely eliminated, and the tires could be run at 1.5 bar (22psi) with complete confidence. Schwalbe's sponsored riders began competing on the system at World Cups, midway through the 2014 season with excellent results. Reportedly, one of the most prominent users is Mister Samuel Hill. Schwalbe and Syntace say that the additional sensitivity afforded by the ability to run lower tire pressures, and the enhanced sidewall stability created by the inner tire being able to support the tire casing above the rim flanges give the rider a huge cornering advantage.

While it would be a stretch to claim that Schwalbe's Procore tire system is largely responsible for Hill's recent domination of the World Cup DH, there can be no doubt that the Australian has owned every off-camber section and slippery corner in the second half of the 2014 season. Hill always keeps his cards close to his chest, but I suspect that the world's fastest man on flats has a secret weapon. It could be a can of old fashioned Whoop-Ass, or it could be Schwalbe's Procore tire system.