Car Walls DefinitionSource (google.com.pk)
This can be seen by consulting the standards published every year by the industry standards group, the Tire and Rim Association. As an example, their 2010 Year Book shows that Load Range C tires may require 35 psi (240 kPa) or 55 psi (380 kPa), Load Range D tires may require 50 psi (340 kPa) or 65 psi (450 kPa), and Load Range E tires may require 65 psi (450 kPa) or 80 psi (550 kPa) to achieve their Load Index and Maximum Loads.This is also the case in the tables published by major tire makers, who do follow these TRA standards and have multiple inflation pressures for the same Load Range in the tires they sell.
It is essential to consult the guides like those just mentioned when making tire substitutions, and to read exactly what is imprinted on the sidewalls of tires. A different size of tire with the same Load Range may require a higher inflation pressure, and may fail in use if under-inflated.
In some cases it may be advantageous to use car or van tires instead of Special Trailer tires, for example the 195/50 R13C with a load rating of 104 is superior to the 155/70 R12 Special Trailer tire even though the Load Ratings are the same. The warning "NOT TO BE USED ON PASSENGER VEHICLES" that the ST tire will have informs the user that such tires are inferior to car tires.
The load index on a passenger car tire is a numerical code stipulating the maximum load (mass, or weight) each tire can carry. For Load Range "B" tires, ETRTO (ISO-Metric) standards specify the load index rating at an inflation pressure of 36 psi (250 kPa) (table Below) while P-Metric standards measure the load capacity at an inflation pressure of 35 psi (240 kPa). The two standards vary slightly with the capacity required for different inflation pressures.
While all ETRTO tires of the same load index will have the same maximum load, P-Metric tires with the same load index may have different load capacities depending on the tire size. The TRA Inflation Tables must always be consulted when comparing the load capacity of P-Metric tires—the Load Index alone is not sufficient. An example: a P205/50R15 Standard Load tire has a load index of 84 and a load rating of 505 kg (1,113 lb) at 35 psi (240 kPa). A P215/50R13 with the same load index of 84 only has a load rating of 495 kg (1,091 lb), also at 35 psi (240 kPa).
ETRTO produces a Standards Manual (current edition 2010) which contains a number of specifications and tables. The load index table (2010 page G7) lists the Load index from 0–45 kg (0–99 lb) to 279–136,000 kg (620–300,000 lb) (although it appears to relate to an inflation pressure of 42 psi (290 kPa) it doesn't specify, but see Load Inflation Table). The Load Inflation Table references the load index to inflation pressures between 22 psi (150 kPa) and 42 psi (290 kPa) at 1 psi (6.9 kPa) intervals which is too large to be included here.
series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China in part to protect the Chinese Empire or its prototypical states against intrusions by various nomadic groups or military incursions by various warlike peoples or forces. Several walls were being built as early as the 7th century BC; these, later joined together and made bigger, stronger, and unified are now collectively referred to as the Great Wall.Especially famous is the wall built between 220–206 BC by the first Emperor of China, Qin Shi Huang. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, and enhanced; the majority of the existing wall was reconstructed during the Ming Dynasty.
Other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration. Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watch towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor.
The Great Wall stretches from Shanhaiguan in the east, to Lop Lake in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. A comprehensive archaeological survey, using advanced technologies, has concluded that the Ming walls measure 8,850 km (5,500 mi). This is made up of 6,259 km (3,889 mi) sections of actual wall, 359 km (223 mi) of trenches and 2,232 km (1,387 mi) of natural defensive barriers such as hills and rivers. Another archaeological survey found that the entire wall with all of its branches measure out to be 21,196 km (13,171 mi).