ROCHESTER HILLS, Mich. (May 21, 2007) — During the first quarter of the year, fleets usually sign their contracts for tire purchases for the rest of the year, dealers re-supply their inventories in preparation for the boom months, but freight right now still tends to be a little slow.
As a result, tires—including new, used and retreaded—tend to end up in storage longer than we'd like. Vehicles that normally are out hauling freight end up parked along the fence in the fleet's yard. What about the tires on those parked vehicles and those in inventory? Are they being properly cared for even though they are just sitting in a warehouse or a yard?
When tires are stored or not used for long periods of time, they should be protected against the evils of the world. Those held in inventory should be stored in a cool, dry place so that water cannot collect inside them. Water should never be allowed to sit inside tires. It's a good idea to place them on a clean, dry surface, protected from wet floors or any other dampness.
If they have to be stored outside, they should always be covered with a tarp or other waterproof covering so that no water can get inside them. Any tires with cuts, stone drills, punctures or other damage should be repaired prior to storage to avoid growth of these injuries due to moisture migration, which could make them unrepairable when you're ready to take these tires out of inventory.
The enemy list
We all know that tires and petroleum products (such as diesel fuel, oil and grease) and antifreeze don't play well together. These products are readily absorbed by some rubber compounds and can contaminate the tire and deteriorate its sidewalls and tread.
Sidewalls can swell, soften, appear spongy, and, in extreme cases, they may become undulated and distorted. Treads can blister and become spongy too if a tire is left to sit in a puddle of gunk.
Therefore, contact with these products and even strong petroleum vapors should be prevented. Optimally, tires should be placed on a clean, dry surface and protected from whatever might get on floors.
Placing them on a pallet, even if it only gets the tires two or three inches off the floor, is a good idea.
Although tires are used to running in bright sunlight and are designed to perform well with normal exposure to heat and light, they should be protected from these elements when stored. If a tire is sitting in one position for a long time, heat and/or light can be concentrated on specific portions of it. This can cause premature weather checking also known as “ozone cracking.”
The severity of the cracking is dependent upon the length of time and the temperatures to which the tire was exposed. However, you should know that excessive exposure can render the casing unserviceable. Therefore, direct sunlight and high heat sources should be avoided as much as possible. If tires are stored outside, they should be covered with an opaque or black polyethylene film. (Not clear plastic.)
Some people believe that it will extend a tire's life, especially mounted tires, if they clean them before storing. However, this is not true. Dirt alone will not hurt a tire, but frequent washing, especially using aggressive cleaning agents, can prevent protective chemicals stored in the tire's rubber compounds from migrating to the surface to keep the tire fresh. It's better for tires' health to run them hard and store them away dirty.
We've all heard that tires should be protected from ozone while in storage. Ozone occurs naturally in the atmosphere, but there also may be equipment that generates ozone located in areas where tires are stored. Tires should be moved away from electric motors, welding equipment, generators, power lines and switches. If exposed to high levels of ozone or in lower levels over an extended time, tires will develop ozone cracking—and if severe enough, this condition can take them out of service.
Covering tires, whether they are stored inside or outside, with opaque or black plastic will not only protect them from collecting water, it also will protect them from ozone generated by electrical sources and cut down on air circulation, which will minimize both the available oxygen and ozone that cause weather checking.
How things stack up
A question many dealers ask is, “How high can I stack truck tires in inventory?”
Unmounted, standard truck tires should be stacked horizontally to a maximum of six to eight tires or three to four wide-base tires.
Mounted truck tires can be stored as high as you can throw them. If this is higher than six to eight tires, I want to meet you!
The point is to ensure that the tires at the bottom of a stack retain their shape and are not squished flat as pancakes. Tires that are distorted are more prone to damage from solvents, ozone and oxidation. Don't forget, it's a good idea to put them on a pallet to protect them from oil, grease and other slime that may be on the floor. The pallets also will facilitate moving the tires if necessary as well as when it's time to put them back into service.
If mounted tires are to be stored, reduce their inflation pressure to 15 psi and place them in an area that is clean, cool, dry and dark.
If you have a fleet that is parking some of its trucks, tractors or trailers until business picks up, advise them to park them on a surface that is firm, reasonably level, well-drained and free of oil, fuel and grease. If a vehicle is parked on an oily floor or even oil-soaked earth, tire treads can be permanently damaged.
If it is anticipated that the vehicles will be stored longer than six months, they should be parked close together facing east or west so that direct sunlight is not focused on the tires. They also should be completely unloaded so only minimum weight will rest on the tires, and the fleet's recommended operation inflation pressure should be maintained in the tires—otherwise weathering may occur.
Stored vehicles should be moved at least every three months to prevent ozone cracking and to prevent a “flat spot” from developing due to strain from the tires' deflection. Usually a flat spot will disappear in a short period of time, but severe tire flat spots may end up being permanent on vehicles stored over six months without moving. When these vehicles are moved, that should be done when temperatures are moderate and never in extremely cold weather.
As business picks up and you need to start taking tires out of storage and putting them back on the road, select first the tires that have been in stock for the longest period of time. This goes for vehicles that have been parked, too. As you can see, the longer the storage period, the more exposure there is to potential damage.
Tires that are unmounted should be closely inspected inside and any debris, foreign material or moisture that may have accumulated in them during storage should be removed prior to mounting. Otherwise, if this stuff stays in the tires when mounted on a vehicle, the moisture will permeate into the casings and wreak havoc with the steel cords, while the foreign debris like screwdrivers, tread depth gauges and old valve cores left in the tires will chew up the innerliners.
Taking care of tires is a never-ending job, isn't it? Just like children, even when you think they are safe at home, you still have to tuck them in at night and lock the door to protect them from the evils of the world.