TIRE INFORMATION

The Department of Transportation requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction, and temperature resistance. These tests are conducted independently by each manufacturer following government guidelines to assign values that represent a comparison between the tested tire and a control tire. While traction and temperature resistance ratings are specific performance levels, the tread wear ratings are assigned by the manufacturers following field testing and are most accurate when comparing tires of the same brand.

Tread wear receives a comparative rating based on wear rate of the the tire in field testing following a government specified course. For example, a tire grade of 150 wears 1.5 times as long as a tire graded 100. Actual performance of the tire can vary significantly depending on conditions, driving habits, care, road characteristics, and climate.

Temperature resistance is graded A, B or C. It represents the tire’s resistance to the heat generated by running at high speed. Grade C is the minimum level of performance for all passenger car tires as set under Federal Motor Vehicle Safety Standards. This grade is established for a tire that is properly inflated and not overloaded.

Note: UTQG ratings are not required on winter and light truck sized tires.

Remember!

Serious injury may result from explosion of the tire/rim assembly due to improper mounting – never exceed 40 psi (275 kpa) to seat beads – mount only on designed diameter rims – only specially trained persons should mount tires.

Tires need to have air pressure checked regularly but it must be done while the tires are COLD!

All tires should have their air pressure checked on a regular basis, preferably weekly for truck tires and at least once a month for passenger car tires.

Truckers and motorists who get in the habit of checking their tires on a regular schedule will experience far fewer tire failures and, as an added benefit, will find that their tires last longer and their fuel costs will decline.

“One of the problems about tires is that they are practically the only part of a vehicle that can be totally abused and the vehicle will keep moving. Seriously under inflated tires will not stop a vehicle. Try driving with no brakes and you’ll see what I mean,” said Harvey Brodsky, Managing Director of TRIB, the Tire Retread Information Bureau. “Because of this, many truckers and motorists tend to ignore their tires, often until it’s too late.”

“By not paying attention to this very important component of tire care, they not only waste money, but they put themselves and others at risk of an unnecessary tire failure,” Brodsky added.

TRIB recommends setting a regular weekly or monthly schedule for checking air pressure. A properly maintained and regularly calibrated tire gauge should be used, and the tires MUST have their air pressure checked while the tires are COLD, preferably having been driven for less than one mile.

The retreadability of truck tires that have never been driven under inflated rises dramatically, which has a very positive effect on a trucking fleet’s bottom line. The best way for fleets and motorists to lower tire costs is to inspect tires regularly for cuts and other signs of irregular wear, and to check tires with a gauge while the tires are COLD.

A good time to check tires is first thing in the morning after the vehicle has been sitting for several hours or longer. This will insure that the tire inspections and air pressure checks are being made while the tires are COLD. According to TMC data it only takes about 20 minutes to check and adjust inflation pressure on an 18 wheeler.

The old saying, TAKE CARE OF YOUR TOOLS AND YOUR TOOLS WILL TAKE CARE OF YOU is especially true when it comes to tires.

Tires are tools (try operating a vehicle without them!) and whether we like it or not, they do require care.

The time it takes to visually inspect and maintain proper air pressure in tires is an investment that fleets and motorists really can’t afford not to make.

Glazier Trucking earns its keep by moving big loads long distances in minimum time. And not unlike typical owner/operators, this Tulsa, Oklahoma carrier pulls its 53-footers behind 260-in. wheelbase sleepers powered by 500-hp diesels.

Glazier maintains its 295/75R22.5 steers at 105psi and drives and trails at 100psi. That combination has proven best for long tire tread mileage and retreadability.

Compare that line haul solution with Murphy Construction, of Appleton, Wisconsin, with its 11-yd front discharge mixers sporting steer axle loads of more than 20,000lbs. Murphy runs L load range 445/75R22.5s up front and airs them from 115 to 120psi. The rest of their mixers’ 73,000 gcw is split up between eight smaller drive tires and two others on tag axils, so they don’t need as much inflation pressure. And these mixers don’t begin to log the kind of road mileage or sustained speeds as the Glazier semis do.

Meanwhile Chicagoland’s Pepsi Cola runs full service delivery trucks in cities’ stop-and-go traffic with 80psi in their LT235/85R16 light truck radials. In this case, six tires together support loads up to 16,000lbs.

Dayton Freight Lines, an Ohio-based LTL carrier, runs 100psi in its steers and 90 to 95psi in its drives while using 295/75R22.5s, the same size that Glazier uses. The difference: Glazier handles maximum truckloads while Dayton specializes in LTL freight and its semis rarely approach 80,000gcw.

Different axle loads, different speed requirements, different service conditions — in determining proper air inflation pressure, all kinds of factors enter into the mix. A semi hauling 50,000 gcw at 65 mph doesn’t need the same tire inflation as a 65-mph vehicle approaching 80,000lbs.

Likewise, an 80,000lb logging truck crawling along a stone-lined gravel trail can get by with 60psi or less inflation pressure until it reaches improved roads and resumes normal speeds. (Goodyear tests have proven you can safely reduce inflation pressures for brief periods if speeds are kept under 35mph. Don’t try that in your linehaul semi at full highway speeds.)

In general, running trucks at normal speeds for prolonged periods with inflation pressures just 20 percent under what is recommended can reduce tire mileage by 16 percent and fuel mileage by 2.5 percent. If you err in inflation pressures, experts will tell you it’s better to be overinflated than underinflated. Extreme overinflation can also lead to other problems though, such as irregular wear patterns and reduced puncture resistance.

Excessive casing heat resulting from under inflation is the culprit. When you run under inflated tires for long periods, the centrifugal load and speed forces build extra heat as the casing flexes, leading to tire fatigue and the ultimate break down in tire structure.

Checking (and correcting psi) in the middle of a hot day or after driving for several hours is a common way to shortchange your tires. During normal service, for example, inflation pressures can increase 10 to 15psi due to increased casing heat. If you bleed out this overage, your tires will be 10 to 15psi under inflated after they cool.

Ambient air temperatures also affect tire air inflation. For instance, your tires will gain 2psi for each 10° F increase in ambient air temperature over 60 degrees. Bleeding out this overage midday with temperatures over 90 degrees could also be a mistake.

Another sure way to reduce tire mileage to removal is to increase your highway speeds without compensating by reducing truckload and increasing tire inflation pressures. The penalty for running 75mph instead of 55 without compensating can be 20 percent in reduced tire mileage.

The benchmark is reduce tire load by 4 percent and add 5psi to your tires when increasing speed from 55mph to 65, 12 percent tire load and 5psi when increasing speed from 55 to 75mph. At the higher speeds, tires flex more and make longer footprints, which can lead to cupping and fast shoulder wear.

All other factors being equal, you can determine the proper air inflation pressure for your tire loads by referring to tables. To use tables, determine the maximum load your tire (single or dual) is likely to encounter. Then, using your tire size/ply rating, find the correct load in the table that is close but slightly more than the maximum you expect. The inflation pressure list at the top of the column is your minimum pressure.

Note that singles and duals have different allowable loads for the same inflation pressure. The reason is to provide a cushion for the surviving dual if its axle partner should fail.

Within the same service application, it’s relatively easy to figure out the proper inflation pressures for your tires based on their axle loads. To maximize tire life, however, you should also bring other considerations to the table. If one shoe doesn’t fit all, nor does one tire… or inflation pressure.

• Inflate for maximum load your tire must carry

• Check psi when tire is cold

• Use flow-through metal valve caps

• Use air dryers in your system to avoid introducing moisture

Most new or undamaged medium radial truck tires can withstand three to four times the recommended pressure before bursting. In fact, the rim usually fails before the tire. ITRA has conducted several burst strength tests on new and used medium radial truck tires with special reinforced rims. The tires were pressurized with water. Most recently, three new tires and 13 used tires were “burst tested” with the lowest pressure burst recorded at 300psi and highest at 540psi for an average of 420psi. All of the test tires failed in the bead area.

The extent of under inflation and the speed and distance the tire ran are factors to consider. Also, under inflation affects tubeless and tube-type tires differently. In fact, it causes so many conditions we think it best to state that under inflation causes damage to all tires and should be avoided. We do not recommend any tire as being better than another when run under inflated.

If the tire is free rolling and not slipping, a wet surface lubricates and cools the contact area of the tire, thereby causing it to wear at a slower rate.

Why is it that the price of fuel for our vehicle seems relatively inexpensive while the cost of its tires seems high? If we keep track of our total costs we will find that typical total fuel costs for just 10 to 20 thousand miles of driving actually exceed our tire costs. And believe us, we’ve found that the quality and performance of our tires has a lot more to do with our driving satisfaction than our fuel does.

We think that much of the misperception has to do with the fact that we buy fuel one tankful at a time, and don’t really look at its total cost for thousands of miles. Our tires are paid for “up front” and then last for tens of thousands of kms.

When you are selecting new tires and find one that is perfect, although more expensive than another tire that appears to be a close second; consider evaluating your situation by comparing “how much per mile” each tire will cost. If you plan to drive your vehicle another 30,000 miles and are considering the “perfect” tires at $100 each, and the other at $90 each; you may be surprised to find out that the cost of the “perfect” set costs just 1.3¢ per mile…while the close set costs 1.2¢ per mile. Will saving the $40 today make up for not having selected the “perfect” tire that you will be driving on for the next two years?