It indicates on that, under the same general conditions, one tire can be expected to produce more mileage than another, not what the mileage will be. Again, actual tread life is strongly influenced by where you live and how you drive. In some parts of the country, tires wear out faster. For example, the local rock used for road construction is rougher in some geographical area than in others. The same tire might give 20,000 miles in one part of the country and 30,000 in another, but a tire with a higher grade should produce better tread life than a lower graded tire in either locality.
Mileage is determined primarily by driving habits.
Drivers who start off slowly can expect the best tread life. Studies have shown that treadwear for the same tire can be as low as 14,000 for some drivers, but as high as 30,000 miles for other drivers in the same geographical area. Proper maintenance is also important. When driving on wet roads, good traction is important to your safety. When the tread is badly worn, all tires lose much of their stopping ability, especially on wet roads.