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Friday, December 5, 2014

The Daily Bike: Schwalbe Reinvents the Mountain Bike Tire | adventure journal

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Back in the late 1990s tubeless tires came along and transformed mountain biking. Tubeless tires let you run lower pressures, so the tires conform beautifully to terra firma, and as a result, corner like high-performance sports car rubber.
But.
But they have a few faults. The primary one is that finding your happiest inflation level is a crapshoot. If you weigh 200 pounds that might be 45 PSI; if you’re 150 pounds maybe it’s 22 PSI. Or maybe not, as a g-out, root, or rock can easily “burp,” or nudge, the tire right off the rim, and there goes all the air, whether you run sealant inside or not.
Schwalbe claims it’s solved the problem with the new Procore tire system, an intriguing and possibly game changing setup. Procore tires have dual air chambers. You run a small inner tube right against the rim at a very high pressure, say, between about 55 and 85 PSI. Then you fit the Schwalbe tire over the inner tube. The funky system has a unique, dual valve: It lets you fill both the inner tube and the cavity between inner tube and tire by adjusting the threading. And that outer cavity, the one that determines most of what you feel rolling along, can be filled to just 10 to 20 PSI.
Schwalbe says the system provides two major improvements. First, the inner chamber prevents burping the tire off the rim wall, since the tube holds the tire bead in place. The tire can’t walk off the rim even if you strike a square-edged bump, because the tube is securing it. Second, running exceptionally low tire pressure in the outer chamber of course provides better cornering grip and more surface contact between tire and the ground...

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