A case could be made for the statement, “the best tires are only as good as their air pressure.” If the correct tire air pressure is not maintained, tires will fail prematurely.
According to Gary Schroeder, director of commercial vehicle and OEM sales for Cooper Tire, “Everyone will agree that the No.1 tip for longer tire life is maintaining proper inflation. The key to a good tread footprint and even tread wear is maintaining proper inflation. The inflation figure should be determined by a scale weight by axle and then using a load/inflation table. Mismatched inflation on dual assemblies is an important contributor to faster tire wear. In an 11R22.5 tire size mounted in a dual assembly with the same new tread design; you would assume that they are the same size with the same circumference. At 5-PSI difference in inflation, the lowest inflation tire has a circumference that is 5/16-in. smaller. During every rotation cycle, the smaller circumference tire must scuff ahead to keep up with the tire with more inflation. These tires rotate around 500 times per mile. Simple math means 500 times 5/16-inches translates to 156.3-in. per mile, or 13-ft. per mile. Imagine dragging a tire 13 ft. every mile. How many feet is that per day or per year? That illustrates clearly why you will see increased tire wear with improper pressure.”
Another note on inflation for those running automatic inflation systems: How often are you checking the inflation and correcting the pressure on these mismatched dual assemblies? Don’t automatically assume they’re running perfect—you need to check on a scheduled basis.
Schroeder goes on to advise fleets to stay on top of tire rotations—especially in areas of irregular tread wear. Tire rotations may contribute to lessening the wear. One of the things that happens when there is a change in the direction of the rotation, or when cross rotating the tires, is irregular wear areas are evened out. Changing the direction of rotation has a tendency to even out heel/toe wear on the shoulders of drive tires and erratic wear on the shoulders of trailer tires. Steer tires are normally rotated side-to-side which again changes the direction of rotation and helps even out wear. At 3/32- to 4/32-in. difference in tread depth between the drive axles, a cross rotation would be recommended to even out the wear and increase tire life before removal. Directional tires would be the only tires that should not change the direction of rotation.
“Maintain the proper inflation pressure based on load,” Schroeder says. “With an 80,000-lb. gross vehicle weight the load/inflation is relatively easy. The typical steer axle is at 12,000-lbs., or 6,000-lbs. per tire. In a 295/75R22.5 tire size; 110 psi cold gets you to 6,175-lbs. in capacity. On the duals at 17,000-lbs. per axle or 4,250-lbs. per tire with the same size 295/75R22.5 tire, the inflation figure at 85-PSI carries 4,690-lbs. per tire. This is not the old ‘100-PSI works for all scenarios.’ You get better wear, longer tire life and fewer impact breaks at this lower inflation figure. Over inflation decreases the resistance to punctures and impact breaks. Over inflation also causes irregular wear, improper handling, ride disturbances, and reduced traction. A load/inflation chart will pay dividends in spades.”
“From Bridgestone Ecopia tires to Bandag retreads, Bridgestone has the breadth of products for a variety of trucking segments,” says Kyle Chen, manager, Bandag Programs, Bridgestone Commercial. “However, fleet managers know that a successful tire program that maximizes the life of casings is the result of not only good tires and retreads, but sound maintenance practices and data. Bridgestone has a complete suite of solutions, from casing inventory management to mobile training and emergency road service programs, that help manage, guide and enhance fleet tire programs of all sizes.”
Some fleets forgo retreading to try inexpensive imported tires under the belief that a low acquisition price means dollars to the bottom line. Many of the largest fleets in the country have an alternate view. They see premium new tires as assets worth maintaining and retreading, which often multiple times, lowers the overall cost of ownership and, as a result, maximizes bottom line benefits.
Smaller fleets want the same benefits but may not have the facilities, the manpower, or resources to effectively manage a top-notch tire program. “That’s where a partnership with a quality tire dealer can really make a difference,” Chen notes.
Common sense care
Kumho says, while it does not offer a National Account program to fleets at this time, its authorized dealers carry the products that meet the demands of fleets coast to coast—and its new tires offer high mileage and the fuel savings fleets have come to expect from Kumho. In addition, the tire maker says its casings offer the fleets piece of mind and a strong warranty.
Kumho also notes that there are many things a fleet can do to increase tire life:
- Determine and run the proper air inflation levels. Incorrect air pressure will cause premature wear and even more costly, an increase in fuel consumption;
- Reduce your top speeds to boost fuel efficiency and decrease tire wear;
- Alignment is key. Irregular wear is most commonly caused by poor vehicle alignments;
- Mount tires correctly;
- Rotate tires;
- Replace tires with tires that match (pattern and tread depth);
- Replace worn wheel and suspension components; and
- Complete a free trip inspection daily.
All of these will help to reduce irregular wear and boost fuel savings.
Using scrap tire data
A scrap tire pile can harbor a treasure trove of information. Scrap tire analysis, or out-of-service-tire-analysis (OOSTAs) as they’re sometimes called, is considered a fleet best practice because it’s a “high-leverage” activity, meaning it pays multiple dividends. Besides recovering tires that are eligible for a warranty credit or that can be repaired or retreaded—saving the cost of buying a new tire—scrap tire analyses can quickly point towards the need for changes in maintenance programs. For example, analysis can highlight tire inflation issues, alignment problems or even the need for a change in tire program specs. These benefits can save fleets money by avoiding unnecessary tire purchases as well as potentially reduce costly downtime.
Chen notes “Data gathered from OOSTAs can be much more useful if fleet technicians mark the out of service tires with key information such as wheel position, truck number, air pressure at removal, etc. This information makes it easier to spot trends such as, a driver training issue, or could lead to route changes.”
By far, the most common cause of premature tire failure is under-inflation resulting from poor air pressure maintenance, overloading or the loss of air pressure due to an operational issue. Evidence of failure due to low air pressure such as a “run-flat” include, a wrinkled or discolored liner, a puncture in the crown or sidewall of the tire or evidence of overheating, which results from the excessive friction a tire generates when there is not enough air to carry the load.
Tracking scrap data
Brake skid wear
Cooper Tire’s Schroeder says, “Scrap tire analysis is an important tool in tracking and evaluating your tire program. By tracking and evaluating your tires, you can minimize tire expenses and improve your bottom line. A monthly scrap tire analysis gives you timely information that can help you see areas in your fleet that need attention, and lead to improved operations.”
“The first step is to have a form to record all of the necessary information to successfully track scrap tires. Roadmaster dealers have these forms, which come with “out-of-service codes” to break the conditions down to operation/service related issues, casing-related issues, program specification issues, repair-related issues, and retread-related issues. Out-of-service codes are provided for each category and there are places to track both new tire brand codes, casing brand codes, and retread brand codes.
The Technology & Maintenance Council’s (TMC) Radial Tire Conditions Analysis Guide is a great resource. This guide provides good photos of tire conditions, which are very helpful, if you’re not an experienced scrap tire inspector. It also gives a list of the causes for the condition. There is also a list of what you should do with the tire, what to do with the vehicle, and what to do in operations—and it covers wear conditions as well as out of service conditions for both original tires and retreaded tires.
Schroeder goes on to say,“What we feel is most important to glean from a scrap tire analysis is operations—or service-related tire conditions. Once identified, these can be corrected. Service conditions would include improper repairs, mounting damage with torn beads, and load/inflation issues. The age of the casings and the number of retreads also needs to be looked at. It is important that your tires are repaired properly. Service personnel either employed internally or by a service provider, must be properly trained to perform repairs that comply with the industry standards and Roadmaster dealers can assist you in this area. Make sure qualified and properly trained service personnel service your tires.
Wear conditions are another place to gain additional information that may help you lower tire costs. The TMC Radial Tire Conditions Analysis Guide breakdowns the wear conditions by steer, drive and trailer positions. Typical causes could be alignment, lack of adequate inflation, improperly matched tires, suspension issues or improper bearing adjustment. Those conditions pointing to an operational or service related issue needs to be researched and corrected. Conditions pointing to a vehicle problem should be corrected before new tires are installed, otherwise the problem will repeat itself. There should be a process in place to get your vehicle maintenance technicians involved with the scrap tire analysis before the new tire replacements are installed. Doing the analysis on tire wear a month or two after the tires were changed means the problem that you had, is already starting to impact your new tires. Course correcting mid-stream might not get your tires back on track.
“What’s more, and this is important, the scrap tire analysis is a great place to look for both original tire and retreaded tire warranty conditions. Check for the amount of tread is remaining on the tires that are out of service? Is this tire a candidate for a warranty refund? Who manufactured this tire or retreaded it? If you have failures relating to older casings in retreaded tires, you may need to narrow the parameters of casing age that is acceptable to retread.”
Scrap tires may not be useless
Some fleets believe that once a tire has been scrapped, it’s useless. This is not always the case. “Over time, the information gathered from scrap tire analysis can help fleets see important trends,” says Andrea Russell, marketing manager, Goodyear Commercial Tire Systems. “This can help them make better decisions about tire maintenance and other key issues.”
Going through a pile of scrap tires should not be a one-person job, according to Russell. “It’s much more efficient to have at least one person move the tires around and another to write down data,” she says.
“Make sure that everyone involved wears appropriate clothes and leather gloves to protect their hands against cuts and scrapes.”
Have at least one large awl available for digging into cuts, nail holes and loose belts. Before delving into a pile of scrap tires, Russell recommends creating a spreadsheet with the following headlines/categories:
Reason/Observation: Briefly describe the reason why the tire is sitting in the scrap pile. A tire that has worn evenly down to 2/32nds, has multiple retreads, and has no holes in it “is most likely a tire that has rendered excellent service during its lifespan,” Russell says.
However, scrap tires sometimes exhibit unusual conditions. “A few of these conditions – such as brake skids and sidewall damage – might stem from the truck operator’s driving style,” Russell says. “Be on the lookout for unusual tread wear patterns.
“Issues like irregular wear can offer glimpses into a fleet’s tire maintenance practices. For example, too many tires with big differences between the wear on one side of the tread and wear on the other side of the tread could indicate that alignment issues are not being addressed, or tire inflation check practices are not what they should be.”
Last Retread/DOT Date: Each time a retreader puts a new tread on a tire, a U.S. Department of Transportation-assigned, two-letter identification code and information about the week and year the tire was retreaded are branded onto the casing’s sidewall.
Tread Depth: Ideally, a scrapped tire should be worn down to the tread level that has been designated as its “pull depth.” Often, when an irregular wear pattern has developed, tread depth measurements can be vastly different, both across the tire’s tread face and around the tire. To record tread depth in a tire that is showing irregular wear, measure the shallowest point in a major tread groove and record this as the tire’s tread depth. Tread depth measurements should be performed at a minimum of two locations around the tire. Making note of tread depth variations will help fleets see trends among tires that might be wearing prematurely.
Number of Retreads: Over the long term, fleets could find that some brands or models of tires within a particular brand lend themselves well to the retreading process—and might discover certain tires can more consistently handle multiple retreading.
New Tire Brand/Type: Knowing the brand and type of the scrap tire is essential to good record keeping. A scrap tire analysis should be able to help tell a fleet what is working and what isn’t. In addition, scrap tire analysis can help fleets choose tires with the right tread designs for their applications. In the transportation business, knowledge is power, and there is a tremendous knowledge sitting in a scrap tire pile.