Tires. Midland End Dump Trailer

5.2.6 TIRES

Tires are one of the most important components on a trailer and must be maintained in top condition to obtain their desired load carrying capacity and durability. Tire wear rate can be used as an indicator of the condition of the axle alignment or suspension system. Poorly maintained tires will wear rapidly or deteriorate and fail quickly and suddenly. A poorly maintained tire can and will affect adjacent components leading to their potential failure as well.

Proper tire maintenance includes but is not limited to:

1. Inflation Pressure:

Operating at an incorrect inflation pressure is the most common maintenance problem with tires.

Tires should be checked frequently to be sure they are at their specified pressure.

It is recommended that tire pressure be checked at the start of each working day and at least one other time during the day. Always use an accurate hand gauge when checking the pressure and check each tire. Carry it with your unit so it is always available when needed. The most accurate pressure is obtained when the tire is cold. Every tire has its specified operating pressure molded into the sidewall. Adjust the pressure as required to obtain the specified inflation pressure when the tire is cold.

Tire pressure will normally increase 10 to 15 psi during operation as the tire heats up. If the pressure exceeds this normal increase, it indicates the tire may be overloaded, underinflated, driven too fast, improperly sized or a combination of these factors. Identify the cause of the problem and correct it before resuming work.

a. Underinflation:

Operating at lower than the specified pressure is a tire's worst enemy. Use an accurate tire pressure gauge to check the pressure at the start of each working day, every few hours during the day and/or whenever the handling characteristics change suddenly. Underinflation will increase tread wear and cause a deterioration of the tire body leading to a separation of the tread from the body. An underinflated tire is soft and deflects more than it should causing fatigue cracks or breaks in the body cord construction leading to sudden air loss.

Operation with a low or flat tire on a dual will generate a lot of heat in the underinflated tire from internal friction that it can and will disintegrate or catch on fire. It also causes overloading of the adjacent tire on the axle or axles and could lead to their failure also.

Overinflation:

Inflating a tire over its specified pressure can lead to serious problems also. Overinflation creates a more rigid tire that does not absorb road shocks as well as it should.

Shock loading from impacting bumps or pot holes can break the fabric of the tire and/or transmit the higher loads into the rim, wheel and adjacent components causing them to fail as well. Overinflated tires cut, snag or puncture more easily than properly inflated tires. Also overinflating tire will not increase its load carrying capacity.

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2. Tire Matching and Spacing on Duals

Tires on a dual assembly must be matched for size (diameter or rolling radius) and type of construction to obtain the desired and expected performance and life.

Matching of Size:

Tire sizes can vary between manufacturers and as they wear. Special care must be taken to be sure the tire size (rolling radius, diameter or circumference) is within the following dimensions:

Rolling radius: 1/8 inch (3 mm)

Diameter: 1/4 inch (6 mm)

Circumference: 3/4 inch (19 mm)

Measure the tire when it is mounted, inflated to its specified pressure and not loaded.

The easiest method is to use a steel tape to measure the circumference of the tire.

Unequal sized tires will require the larger tire to carry more of the load and potentially overload it. Overloading accelerates the wear and can lead to tire failure. When the one tire fails, the remaining tire or tires will then also be overloaded. The smaller tire will not contact the road surface properly and will wear in an irregular manner giving poor durability.

Tire Construction:

Customers can use radial or bias ply tires on their trailer. However, it is recommended that different types of tires not be mixed on an axle. Each type of tire has different deflection, cornering and spring characteristics. These differing characteristics cause the tires to always fight each other during operation and will give erratic handling and poor wear characteristics when mounted on the same axle. Different types can be mounted on different axles but not on the same axle.

ROLLING RADIUS

Fig. 56 TIRE DIMENSIONS

Tire Spacing:

A wide variety of rims can be used on the trailer and each will provide a different offset.

Select the rims to provide sufficient space and clearance between the sidewalls of the tires. Normally there should be at least

2 inches (50 mm) and 3 inches (75 mm) between the sidewall of a bias ply and radial dual tire assembly respectively. This spacing will provide sufficient clearance for each type of tire to deflect as they rotate and when they impact a pothole or bump in the road. If they touch during operation, they will wear or abrade at the contact point. In addition, tires that are too close do not shed dirt, trash or stones that can get between them during operation as well as properly spaced tires.

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