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Judging from viewpoint of automotive safety and more space by eliminating a spare tire, the development of the run-flat tires is important. Many problems relating to weight increase and usability had to be solved in the course of the development of such tires. The “ N ” type run-flat tire, described in this paper, has a simple structure with reinforced side walls and additional beads to fit the rim flanges. Though this tire system brought about a small amount of weight increase, it needs no special part, therefore the conventional road wheels, air valves and tire changers may be used. We have tested and evaluated this tire system equipped with passenger cars as well as on the test machines. Especially vehicle dynamics such as steering, stability and so forth were tested. The test results indicated that this tire system is practical enough.

This paper describes two types of tire pressure warning devices, TWD-I and TWD-II, that are low in cost and are easy to install on a vehicle. TWD-I has a buzzer and a dry-cell battery that are attached on the inside of the wheel center cap. They are connected to a pressure switch that is attached to the air valve stem after the tire is filled with air to the prescribed pressure. If the pressure drops below a certain level, the switch sends a signal that energizes buzzer. TWD-II is a kind of monitor that indicates a drop in tire pressure by changing the color of the wheel center cap through the action of a diaphragm and a magnet. In comparison with conventional innovations, the two new warning devices offer the advantages of lower cost and easier installation on vehicle.

Basic vehicle performance, such as Safety, Comfort and Economy, are by dependent on tire performance, and it is the air pressure in the tire which assures this performance. However, tire air has a tendency to leak naturally, making it necessary to check them periodically. Since a deterioration in vehicle performance resulting from a drop on tire air pressure can not be directly felt by the driver, the number of people maintaining their tires sufficiently is relatively few. There have been many tire pressure warning devices developed which advise the driver when the pressure drops below a prescribed level. Differing from conventional devices, the TWD-III features a 7-step digital display (at a pitch of 0.1 kgf/cm2) which shows the pressure of each tire within an optional range, and it also has a flat tire warning function. The employment of echo effect from clystal vibrator resonance precludes the need to attach a power source on the tire.