1. Introduction tire
flat tires study called “run-flat tires 
.” Abbreviation RSC. Rear wall of a pneumatic tire is the primary site to support the weight of the vehicle, in particular a number of flat ratio (flatness ratio is the ratio of height to width of the tire) larger tire sidewall very “Hypertrophy”, “tire” usually serious resulting in instantaneous collapse of the tire wall, so that the tires instantly lose support force, causing the vehicle center of gravity changes at once, especially front-wheel drive car front tire after a puncture focus shifted moment is likely to make the vehicle out of control.
If the driver does not tire driving experience (most people do not), you may do wrong driving maneuvers (eg brakes), which will result in irreparable loss of control of the vehicle.
flat tire is a very serious security incidents, particularly flat tire on the highway. According to statistics, the domestic highway traffic accident by 70 percent due to a puncture, which occurs above 160 km per hour mortality rate is close to 100 percentage puncture.
to the vehicle configuration “flat tires” security problem is solved greatest degree of concern. But truly be called the “flat tire” is the military 6times; 6,8times; 6 armored vehicles and other off-road tires, tire in their specially designed metal strip, even in the face artillery shrapnel breakdown can be maintained tires will not deformed and move on. Ordinary civilian “flat tires” Although not do so tough, but the “explosion” principle is basically the same.
2, the development process of
BMW 7 Series equipped with the first RSC flat tires
In 2001, the fourth generation of the BMW 7 Series to market. In addition to the 7 Series weird shape, maddeningly complex of idrive electronic system caused controversy outside people, it is equipped with a flat tire in the first production models, enough to cause concern. In 2005 domestic new 3 Series first appearance, BMW also put this high-profile technology called RSC flat tires to the market, when toToday, the full range of BMW models are equipped with RSC tires. It differs from the
RSC tire and conventional tire including explosion proof, reinforced sidewalls, an additional valve strip and the high heat resistance of a synthetic rubber material. Vehicle speed
RSC with the tire deflated, the vehicle can still be 80 km / h traveling 250 km. But enough! RSC has avoided major accidents in the highway would lead to almost flat tire, but you can avoid risky situations to change a tire on the highway. Even under emergency situations, there is no time to change tires after a puncture, runflat tires can also support you travel 250 km.
The reason why the flat tire RSC not collapse after discharge, mainly because the rubber thickened sidewall, even if the pressure loss, it is possible to support the weight of the side walls of the vehicle, does not lead to severe deformation, so the rear tire puncture and will not seriously affect the running of the vehicle, there may not feel even the owner.
In order to prevent the deformation of the tire from the rim, the rim is specially designed, the peaks of the tire from the rim can be prevented after the sudden drop in pressure. The vehicle is equipped with flat tires, while small discouraged occur, the owner may not notice, therefore RSC also includes the installation on the rim TPI electronic warning system, once the tire pressure begins to drop, RSC immediately issue a warning to the driver. After all, insufficient tire pressure is always dangerous.
BMW RSC run-flat tires are Continental (Horse brand) product, its design principle is to use anti-puncture solid side walls to provide support. And another flat tire design, it is a device which is called a fixed mounting ring, the retainer ring can be supported from the inside of the tire so that the tire will not be crushed, while preventing the tire from the tire washer on shedding. Michelin setbacks
each tire brand has its own flat tire technology, including Goodyear, Pirelli and Michelin. As one of the world tire giant Michelin, in the development of explosion-proof tire has suffered a setback.
In December 2007, Michelin announced that it would stop developing PAX run-flat tires and wheels of the system. Mr. Michelin, president of research and development technology center Philippe Denimal said: Today we are not prepared to develop new PAX system simply because not a lot of market demand, and now the market needsLack of demand, not enough to fill in this technology costs.
Michelin announced as early as in 1997 the market PAX system, PAX system is very advanced, it is the hub by the tire, a special wheel, the support ring and the pressure built detector composed of four parts. In particular, it must have outwardly from the bead anchored specially designed mounting rim, the rim when the tire is mounted on the vertical rim, as can be specially designed to tire bead rim card image clip on.
PAX tire pressure detector equipped with the same, is able to send a signal on the instrument panel when deflated in order to prompt the driver. PAX run flat tire system after the tire without damaging the tire and the rim does not affect driving safety, and also speed of 80 km per hour to 200 kilometers. PAX to the safety and comfort, so like the Audi A8, Rolls-Royce and other top cars are PAX.
But the problem is always there, PAX is not a tire, but the entire system is called “system” because this is not just an ordinary tire tire but by the wheels and tires together form a associated with each other as a whole. Specially designed wheels make the promotion even more difficult, but also increases the manufacturing costs.
Another reason is deadly, PAX system launch in 2005 will increase 25 percent by weight than regular tires, which is more than four PAX tire is equivalent to the weight of a spare tire out, so that was canceled due to explosion-proof tire equipment fetal weight reduction design is no longer meaningful.
3. The technical principle
Although relatively low, statistics show that the probability of occurrence of tire damage, but a flat tire is one of the unpleasant experience of most drivers, now, BMW has become the world’s first manufacturer to provide customers with explosion-proof tire system components (RSC) is. RSC is a set of tire safety component that enables the tire probability of occurrence of risk and drivers of this leak fears have become the past.
RSC RSC tire comprising an electronic warning system and TPI EH2 mounted on the rim. Once the tire pressure began to drop, RSC immediately issued a warning to the driver, but even if the tire pressure drops to zero,RSC able to ensure safe tire fixed to the rim, the tire continued to travel a certain distance. In this way, no longer need to place the spare tire, repair kit and car jack the vehicle, but the driver does not need personally to change tires on the roadside. However, at the same time, RSC can still, if necessary, to continue to ensure the safety of 100 percent.
Because the rim hump through a specially designed, EH2 (broadened peaks) of the rim after the tire is possible to prevent a sudden drop in pressure from the rim. RSC tire differs from the conventional explosion-proof characteristics of the tire comprises a strengthening of the side walls, the additional valve strip and high heat resistance synthetic rubber material, according to the vehicle load, that can be self-supporting tires to minimize the pressure in the case where the vehicle at maximum speed of 80 km / h continues traveling 50-250 km.
In all tire breakdowns, only 20 percentage tire pressure or a sudden decline rapidly. In other words, 80 percent in the case of a tire pressure drop is a slow gradual process, but this time, the RSC tires to continue the vehicle can travel up to 2,000 kilometers or 1,200 miles. Therefore no exaggeration to say, RSC tire itself is its own spare tire. This security is also a significant improvement in that the antilock braking system ABS, ASC automatic stability control system, DSC dynamic stability control system remains fully functional.
RSC system comprising a tire pressure monitor (TPI) and the air pressure of each tire is monitored continuously by comparing the speed of each tire. When the speed over 15 km / h, the tire pressure drops more than 30 percentage, if the rotational speed of a tire of the irregular variation occurs, the system will alert the driver alert by warning lights and audio signals.
However, it is necessary to explain this: TPI is not a substitute driver to regularly check tire pressure. After each change in the tire pressure or a new tire is mounted, the driver need to follow a simple and convenient procedure TPI will reinitialize the system, so as to save the tire data.
RSC technology has brought great advances for the safety and comfort. Even in the case of tire pressure completely disappeared, RSC still allows the driver to continue driving the vehicle at a moderate speed, without a flat tire and had to because in some places there is a potential risk of accidents parking, such as narrow and dangerous placeHome, on the corners, road construction on highways, tunnels and so on. The driver can drive the vehicle
not too far to the maintenance center (not necessarily the nearest service center), then in a more secure way the tires replaced by a service technician workshop, which avoids the replacement of tires personally It occupied the time and inconvenience. Finally, but equally important point is that the vehicle no longer need to place the spare tire, car jack and tools needed to replace other tires, which means that the vehicle load weight, can improve vehicle performance and reduce fuel consumption.
BMW 320i standard with a mounting alloy wheels 205 / 55R16 tire, 325i and 330i, and use 225 / 55R17 tires.
4, the future trend
Michelin PAX problems encountered, all flat tires manufacturers have encountered, so that when the new millennium had flat tires pretty hot, but cool in recent years down. BMW is not smooth sailing in the promotion of RSC flat tires, it’s still not fully understood.
early RSC run-flat tires, the sidewall reinforcement to make comfort greatly reduced, and even affect the vehicle’s handling performance, which will seriously affect the image of BMW luxury sports car. After several years of efforts, the performance horse brand RSC flat tires have been very close with ordinary tires, and its outstanding security has been accepted.
but in terms of price, RSC run-flat tires are still a lot more expensive than regular tires, a tire RSC BMW 3 Series, 4S shop may offer more than 3,000 yuan! And expensive explosion-proof tire life but with ordinary tires, which gives the owner the cost increase.
Not only that, RSC tires due to the strong side walls, if you do not use professional tools to change tires are not replaced, incorrectly replaced even damage the rim, which gave maintenance of vehicles increased the difficulty. Equipped with RSC tires BMW cars, spare tire design are used to cancel.
RSC tire after running 250 km to support the vehicle, if the actual encounter greater damage (e.g., a large area of sharp objectsPuncture) or poor road surface condition, mileage may be reduced to several tens of kilometers, while in the range of about 100 kilometers, you want to find a BMW 4S shop, or is replaceable RSC tire repair shop, in the vast mainland China is sometimes not an easy task.
In any case, flat tires continues to be one of the most important direction for future development of automobile tires, because it brings the security and convenience that people need. As technology advances, the cost of flat tires will eventually come to a reasonable stage.