Abstract: A motorcycle tire is provided with crown main oblique grooves disposed on alternating sides of the tire equator and each extending from its axially inner end to its axially outer end, without cutting across the tire equator, while inclining to one circumferential direction, wherein the axially outer end is located outside an upstanding tire's ground contact annular zone. When measured in the annular zone, the circumferential distance between the circumferentially adjacent crown main oblique grooves existing on the same side of the tire equator is in a range of not more than 0.5 times an upstanding tire's ground contact length. In the annular zone, the crown main oblique grooves on one side of the tire equator is partially overlaps those on the other side. When measured in the annular zone, the circumferential length of the crown main oblique groove is less than the upstanding tire's ground contact length.

Abstract: A motorcycle tire comprises a tread portion provided with first T-grooves and second T-grooves arranged and oriented alternately along the tire equator. The angles of the main portion and branch portion of the T-groove, with respect to the tire circumferential direction, are gradually increased toward the tread edges. The axial distances of the branching point and an inside end of the main portion are not more than 25% of the axial distance of the tread edge, each measured from the tire equator along the tread surface. The circumferential distance from the inside end of the main portion to the circumferentially adjacent T-groove is 5 to 15% of the circumferential pitch length of the first T-grooves.

Abstract: A motorcycle tire is provided with crown main oblique grooves disposed on alternating sides of the tire equator and each extending from its axially inner end to its axially outer end, without cutting across the tire equator, while inclining to one circumferential direction, wherein the axially outer end is located outside an upstanding tire's ground contact annular zone. When measured in the annular zone, the circumferential distance between the circumferentially adjacent crown main oblique grooves existing on the same side of the tire equator is in a range of not more than 0.5 times an upstanding tire's ground contact length. In the annular zone, the crown main oblique grooves on one side of the tire equator is partially overlaps those on the other side. When measured in the annular zone, the circumferential length of the crown main oblique groove is less than the upstanding tire's ground contact length.

Abstract: A motorcycle tire comprises a tread portion provided with first T-grooves and second T-grooves arranged and oriented alternately along the tire equator. The angles of the main portion and branch portion of the T-groove, with respect to the tire circumferential direction, are gradually increased toward the tread edges. The axial distances of the branching point and an inside end of the main portion are not more than 25% of the axial distance of the tread edge, each measured from the tire equator along the tread surface. The circumferential distance from the inside end of the main portion to the circumferentially adjacent T-groove is 5 to 15% of the circumferential pitch length of the first T-grooves.

Abstract: A tire system for motorcycles comprises a pneumatic tire having a cavity, an annular tire core made of an elastic closed-cell material disposed in the cavity and provided on the radially inside with a groove, and a pressure bag inserted in the groove, wherein: in a free state of the tire core not disposed in the cavity, the cross sectional area Sa of the tire core is in the range of from 3.1 to 4.8 times the cross sectional area Sb of the groove; and the total Sa+Sb of the cross sectional area Sa of the tire core and the cross sectional area Sb of the groove is in the range of from 1.0 to 1.3 times the cross sectional area Sc of the cavity.

Abstract: A motorcycle tire comprises a carcass composed of a low-modulus layer disposed along the inside of the tire and a high-modulus layer disposed outside thereof, the high-modulus layer comprising a high-modulus ply, and the low-modulus layer comprising a low-modulus ply. Preferably, the cords of each ply are inclined at a bias angle of from 20 to 50 degrees with respect to the tire equator so that the carcass has a bias structure. The low-modulus layer is composed of two low-modulus plies of low-modulus cords extending between bead portions through a tread portion and sidewall portions and turned up around a bead core disposed in each bead portion. The high-modulus layer is composed of a single high-modulus ply of high-modulus cords extending between the sidewall portions through the tread portion and terminated at a position radially outward of the bead cores but radially inward of the maximum width position of the carcass.

Abstract: A control system for variable speed hydraulic turbine generator apparatus comprises an induction generator connected at its primary side to an AC power line system, a secondary excitation controller connected to the secondary side of the induction generator and being responsive to a generator output command signal supplied externally to supply to the induction generator an excitation current which causes the induction generator to generate AC power at the same frequency as that on the AC power line system, a hydraulic turbine for rotating the induction generator, a guide valve for regulating the amount of water supplied to the hydraulic turbine, a rotation speed detector for detecting a rotation speed of the induction generator, a rotation speed command calculator for receiving a hydraulic turbine running condition signal inclusive of the external generator output command signal and calculating an optimum rotation speed command, a rotation speed controller for comparing the optimum rotation speed command with