TIRE MANAGEMENT: Keep your tires looking new with these simple tips.
TORONTO, Ont. – Today’s tires are tough – almost too tough. They can take an enormous amount of abuse and still survive.
But neglecting tires can be quite costly.
Following the procedures included below will lower your per-mile tire costs through extended tread life, fewer premature removals, and better retreadability
1. Determine proper inflation levels for your application: The biggest influence on tire life is inflation pressure.
At normal speeds, running tires at 20 per cent under recommended pressure reduces tire mileage by 16 per cent and fuel mileage by two per cent. Tires are designed to run at specific pressures based on the total load.
To determine the correct air pressure for your tires, gather information on your actual axle loads and refer to tire load charts. Tire manufacturers make standard load charts are available.
If you operate at higher or lower speeds, use the listed formulas to make the adjustments. In general, pressures need to be higher if the truck is operated at a higher speed.
2. Establish a good inflation maintenance program: Tire pressure is difficult to maintain because tires naturally lose air.
The leakage can occur through valve caps or through small punctures. To stay on top of “normal” leakage and watch for any rapid leaks, tires should ideally be checked once a week by drivers or mechanics. That can be tough if your trucks aren’t in the shop at least once a week or if your drivers are reluctant to comply.
But there are ways to promote frequent checks. A growing number of fleets are using flow-through valve caps which make it easier to check pressure and add air without removing the valve cap.
Other fleets give drivers an incentive to check pressures by conducting random checks on trucks and rewarding drivers if the pressures are correct.
Note that changes in ambient temperature will affect tire pressures. For every 10-degree F decrease in temperature, the pressure will drop two psi. So, during the colder months of the year, tires will need to be checked and inflated more often.
3. Reduce your top speeds: High speeds generate more heat and accelerate tire wear. Goodyear data shows that increasing highway speeds from 55 mph to 75 mph can reduce total tread mileage by 20% or more.
So a tire that would have provided 250,000 miles in tread life at 55 mph will only net 200,000 miles per tread if driven at 75 mph.
The drop is quite consistent as speed increases. That 250,000-mile tread drops to 237,500 miles at 60 mph; 225,000 miles at 65 mph; and 212,500 miles at 70 mph. There’s an added bonus for slowing down: Fuel economy tests have shown fuel usage increases 0.1 mpg for every mph over 55 mph.
4. Keep vehicles properly aligned: Irregular wear is most commonly caused by poor vehicle alignment. It’s simple physics.
If tires are not running straight ahead, accelerated tread wear occurs on parts of the tire. For example, steer axle toe-out will cause excessive wear on the inside of both tires while toe-in will cause wear on the outside shoulders of the tires.
Ideally, most steer tires should have a small amount of toe-in. To maintain this, as well as stay on top of other types of irregular wear, the vehicle should be aligned regularly. Starting a serious alignment program after having none can increase tire mileage by as much as 30 per cent.
While the focus has traditionally been on front end alignment, drive axle and trailer axle positioning can also have a significant impact.
Fleet experience has shown that correct alignment of drive and trailer axles can extend total mileage by 25 per cent as well as improve fuel mileage 0.5 to 1.0 mpg.
More information on effective alignment schedules is available in Guidelines for Total Vehicle Alignment from the Technology and Maintenance Council.
TMC also offers information on the causes of irregular wear in its Radial Tire Conditions Analysis Guide. Both publications are available online at www.truckline.com/store.
5. Mount tires correctly: The rounder or more concentric the tire, the better it will wear.
To keep tire run out to a minimum, they should always be mounted on the wheel correctly. Ideally, the tires should be match-mounted to the wheel.
Wheels are usually marked to show the low spot and tires are marked to show their high spot. How the high spot is marked will vary from one tire to another. Check with the tire manufacturer to see how they mark their tires. The idea is to take the high spot of the tire and match it to the low spot of the wheel. If you mount properly you don’t really need to balance the tire.
6. Learn to “read” tires: Drivers typically don’t check tread wear unless they are having ride problems or the truck is pulling one way or another. By then, it’s often too late to prevent premature wear.
Regular inspections of tires can provide a lot of useful information and catch wear trends before they have done too much damage. Problems can be diagnosed by visual inspection or by running a hand over the tread and feeling for abnormalities.
Items to check for include distortion in the tread, feathering, or cupping. If corrected early enough, bad wear patterns can be countered and tire life can be extended.
At the first sign of it, the vehicle should go in for an alignment. While a person is feeling the tread, the entire tire should also be inspected for safety-related damage such as cuts, cracks, blisters, or bulges.
If the damage is severe enough, the tire will need to be removed.
7. Rotate tires: Moving tires around takes time and effort. The temptation is to leave them in one position for the life of the tread. But intelligent tire rotation promotes even tread wear and can net a lot of extra miles in tread life.
Some fleets will run new steer tires in the drive position and take off 1/32 to 2/32-inch in tread depth to establish a good wear pattern.
Drive tires should be rotated between forward and back positions at least once to even out wear. Rear tires of a tandem typically will wear quicker than the forward positions.
Some drive tires will also develop heel and toe wear. This can be evened out by reversing their direction.
8. Replace tires with matching ones: For optimum tread wear, tires should be as alike as possible across the same positions. If a tire must be pulled due to irregular wear or a road hazard, it should be replaced with a tire which matches the existing one.
The more you can do to eliminate variation, the better your tread wear will be. On dual assemblies, the outside diameters and tread depths should be as close as possible.
A good rule of thumb is no more than 2/32-inch tread depth difference between duals. It’s also wise to have the same tread design on both positions of an axle.
9. Check and replace worn wheel and suspension components: These can be the hidden enemies of tire life. A wheel bearing which is not properly torqued can cause irregular tire wear.
Worn shock absorbers can create depression wear on treads and an early trip to the retreader or scrap pile. Fleets will often wait until suspension components are obviously broken or are leaking before they replace them.
By then, the tire damage has already occurred.
To prevent irregular tire wear, you should be replacing shock absorbers and other suspension components on a set schedule rather than waiting until they fail.
10. Keep good tire records and use the data wisely: Because every fleet is different, there are no hard and fast formulas for tire management.
In fact, copying another fleet’s practices may do more harm than good. To manage most efficiently, regular collection of data on your tires is critical.
You should be recording information including tire inflation pressures, wear trends, and tire mileage at removal.
Using software such as Goodyear’s TVTRACK, you can analyze tire performance and make comparisons with different vehicle configurations and tire types.
By changing specifications, you may be able to realize significant gains in total tire mileage and other performance goals. It all starts w
ith good data.
The more consistent and accurate you are with data gathering, the better the information generated.
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