![]() ![]() Two other significant threats to steer tire performance are misalignment, which results in uneven wear, and under inflation, which causes excessive casing heat, thus reducing the tire’s retreadability or possibly leading to something far more serious: an on-road failure. Instead of running steer tires down to 6/32 of remaining non-skid, and more than 100,000 miles before removal, you might get only 70,000 miles out of them before you have to remove them for worn shoulders, while the center portion of the tread may have more than 10/32 of remaining non-skid. It should come as no surprise that the most frequent steer tire problem is fast shoulder wear, which can lead to cupping and early removal of the tire. Since the footprint is uneven, there is more scrubbing and wearing away of the shoulder rib. With light loads, the tires contact area is quite long in the area of the center tread rib and much shorter toward the shoulder rib. or less) are more prone to irregular steer tire wear than those with heavily loaded front ends. The tiremaker also said tests have shown that vehicles with lightly loaded steer axles (10,000 lbs. While side forces on steer tires can accelerate tread wear, higher loads on steer tires can actually help even tread wear by providing a larger, squarer footprint where the tire contacts the road surface. Setback axles are typically at 42 to 44 degrees. For many years, the standard industry wheel cut angles have been between 32 and 34 degrees. ![]() The setback axles also incorporate increased wheel cut angles, which add to steer tire scrubbing when turning. One H-D truck tire manufacturer said their studies have shown that tires on a tractor with a 140-inch wheelbase must generate about 65 percent more cornering force to slide the tandem drive axles around a corner than steers on a 210-inch wheelbase tractor. But, that also increases side forces on tires during turns. Setback front axles, typically 13 inches to 15 inches back from the standard position, are designed to improve weight distribution as well as the trucks turning circle. Since drivers tend to turn more sharply to the left (sight side) rather than to the right (blind side), the right steer tire tends to get scrubbed the most. Side forces away from the direction of the turn cause scrubbing across the tread surface, which leads to rapid tread wear, particularly on the outer rib. These forces are at their greatest during hard cornering or in an emergency turning maneuver. Every time the driver turns the wheel, the steer tires encounter significant lateral forces as they fight the tendency of the trucks tandem rear axles to go straight ahead. While the steer tire has to be strong enough to carry the weight, it also has to be tough enough to handle scrubbing. An individual drive or trailer tire may carry less than 4,500 lbs., while a steer tire is usually asked to carry 5,000 to 6,000 lbs. These tires usually carry more load than any other tire on the vehicle. Steer tires typically receive a lot of attention from drivers. ![]() Steering Truck Drivers in the Right Direction If a thicker oil is used in some of todays high-tech, small clearance engines, oil pressure may increase, but the possibility of improper lubrication can result if the oil can not adequately flow through the engine.Įngine manufacturers carefully select the recommended motor oil viscosity grade for each specific engine, which is why the owners manual recommended viscosity should always be used. The second number, 30, indicates how well the oil will flow when heated to 100C/212F or higher.Īs engines have become more technologically advanced, engine clearance levels and viscosity grade recommendations may have been reduced, hence the reason your father swore by SAE 20W-50 and your engine calls for SAE 5W-30. The W in the designation is commonly thought to represent weight, but in fact stands for Winter. A 5W, like in SAE 5W-30, can be pumped at an even lower temperature, and a 0W, like in SAE 0W-30, will pump at the lowest tested temperatures. In regard to multigrade oils, the first number in the code, such as 10W in SAE 10W-30, means that the oil can still be pumped by the engine at a temperature as low as a single grade 10W oil. Likewise, the higher the number, the thicker the oil. In single grade oils, the lower the number, the better it flows at cold temperatures. The Society of Automotive Engineers (SAE) developed a grading system to designate the viscosity level of single grade and multigrade motor oils. When referencing motor oil weight, you are actually referring to the viscosity grade or the tendency of a liquid to flow slowly or quickly. To better understand the numerical code used, a brief explanation is in order.
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