TIRE CARE AND SELECTION FOR SURFACE MINING OPERATIONS

Tire life can be increased substantially through effective operating, maintenance, and tire
selection procedures. Surface mining operators who operate from a permanent, fixed base of
operations can develop programs and facilities that increase tire life more than 50 percent.
Some of the factors affecting tire life, in order of most prevalence and frequency, are as follows:

1. Improper road and dump maintenance
2. Bad driver practices
3. Excessive haul speed
4. Overloading
5. Improper tire maintenance procedures
a. Overinflation
b. Underinflation
c. Tire repair
6. Cutting
7. Wrong tire selection

Haul Road Maintenance

Proper haul road construction and maintenance are important for adequate tire life. Equipment
operators should operate vehicles within haul road design limitations. Curves should be posted
with proper speed limits, and be of such radius as to allow for specified speed limits. Flat curves are generally used in quarries, and should carry the following speed limits, to avoid tire ply separation:

Poorly drained roads allow water to fill chuckholes and depressions, hiding rocks and other
obstructions which can bruise or burst the tire from impact shock. Good drainage reduces haul
road maintenance and reduces formation of chuckholes.

Loose, sharp rock fragments are usually encountered in the loading and dump areas, and are the result of spillage from a loader or truck. Overloading a truck results in loose, sharp rock
fragments dropping on the haul road. Periodic dump and haul road maintenance with motor
graders is the best method of reducing the potential hazard.

Loose surface or spilled material causes wheel slippage or spinning on long haul grades, which, in turn, cuts and rapidly wears the tires.
Road surfacing is also an important tire wear factor. Abrasive and sharp road surface materials
cut and wear tires rapidly. Proper grade surfacing material should be used. Predominantly coarse material compacts slowly, and initially causes bruising and tire slippage. Once the material is compacted, rough, sharp, large fragments can cause tire damage. Various types of sands, gravels and crushed rocks are naturally abrasive due to geologic makeup.


Operator Driving

Bad driver practices are responsible for many tire failures. The driver should operate the vehicle in accordance with haul road conditions. Posted speed limits should be maintained, and the speed that road conditions dictate should be used. Road conditions do change and sometimes alertness is required. Obstacles such as sharp rocks, boulders, rock fragments, and chuckholes should be avoided. Tire slippage and spins should be held to a minimum. Fast starts, fast stops, fast turns, and loads that are too heavy can cause excessive wear to tires.

Tires should not be allowed to rub against banks of haul roads or barriers and guardrails that are erected to facilitate spotting and dumping. Excessive braking transfers heat from the brake to tire beads and the inner liner, thus causing potential tire failure from cracking. Proper use of retarders on long grades increases brake life and minimizes heating of brakes.



Tire Maintenance and Repair

Tires should be checked for rubbing against any part of the vehicle. Stones frequently become
wedged between dual tires and should be removed immediately. Many quarries operate trucks
with broken rock ejectors, which are designed to remove stones. Dual tires should be properly
matched. New tires should not be mounted alongside worn tires. The size difference causes the
larger tire to be overloaded.

Tires should be repaired as cuts and snags are detected. Water, dirt, stones, etc., enter exposed
cuts and snags, extending into the cord body, causing tread and ply separation. Rubber becomes soft and spongy when exposed to gasoline, grease, and oil. Washing tires with gasoline or parking in puddles of oil should be avoided. Uneven brakes, poorly aligned, wobbly or bent wheels, or bent axles also cause abnormal wear.
Proper inflation is necessary. Underinflated tires flex excessively and build up tire heat, causing flex breaks, radial cracks, tread and ply separation, and tread shoulders to contact the ground.

Overinflation reduces tread contact with the ground. This causes the center to wear down faster than the tread shoulder. There are less flotation and traction as the tire digs into soft ground.

Overinflated tires tend to skid and spin easily. The tire is hard; thus, it cuts, snags, and breaks
from impact easily. The driver experiences a harder ride, fatigues easily, and has more load
spillage occurring.
Tire cutting can result from spillage, loose surfacing material, overinflation, and careless
operating techniques.Tire manufacturers advise that 50 percent of all off-highway tires wear or
fail because of rock cuts and tread separation. Most of these failures occur in rock quarries and
gravel pits.