Admittedly, I think too often about tires. I was excited to talk to the guys from Schwalbe, at NAHBS 2015, about their ProCore System.
As seen below, the ProCore System an outer tire (like your normal tire), an inner tire (the blue, smaller tire inside the normal tire), a tube inside the inner tire, and a valve that can fill both the tube and the space between the inner tire and the outer tire.
An analogy is that the ProCore System would be like running a tubed, high pressure road tire inside your low pressure mountain tire.
The innovations that allow the ProCore System to come to market are described in US 20150090385, which published on April 2, 2015. When the first systems were being talked about, they had 2 stems – one for each of the air chambers. This would have required to users to drill a second valve stem hole in their rims or rim manufacturers to provide special rims for the system to work. Schwalbe came up with a two-way valve stem that is capable of filling both the tube and the air chamber between the inner tire and the outer tire.
a two-way valve, wherein a first outlet of the two-way valve is in communication with the interior space of the tube, and a second outlet of the two-way valve in the mounted condition is in communication with the air duct between the rim and the tube, and between the tube and the inner tire up to the through opening in the inner tire
Another innovation provided to ensure that both air chambers are fillable is the ProCore Air Guide, which provides a path from the valve stem to the air chamber between the inner tire and the outer tire.
The inner tire and tube not only protect against pinch flats, they also help keep the beads of the low pressure outer tire in place to prevent burping.
Typically, the tube 233 of the tire assembly according to the invention is filled via the two-way valve 238 with a comparatively high pressure, for example, 6 to 8 bar. This is to ensure that the tire beads 230, 232 of the inner tire 228 are pressed outwards with high force, in FIG. 22 to the left hand side and the right hand side, respectively, and thereby, the tire beads 220, 222 of the wheel tire 214 are as well pressed outwards against the rim edges of the rim 210. This is to ensure that the tire beads 220, 222 of the wheel tire 214 do not disconnect from the rim edges of the rim 210. Such a preload force on the tire beads 222, 220 of the wheel tire 214 allows to fill the intermediate space 234 between the inner tire 228 and the wheel tire 214 with not more than a very low pressure, for example, in the range of 1 bar. Thereby, the wheel tire 214 can provide a very high traction without a risk that the tire beads 220, 222 disconnect from the rim 210 upon occurrence of the severe deformation to be expected of the wheel tire 214.
FIG. 1 of the application illustrates the basis of the technology, similar to the above graphic from Schwalbe.com.
I ride some pretty rocky trails out in western Maryland and could benefit greatly from this system even in cross country riding. Looking forward to this tech hitting the market!