ROCHESTER HILLS, Mich. (March 18, 2002)-Right now you're reading a special issue of Tire Business that is dedicated to the commercial tire segment of the industry.
This part of the market has had a really tough year and is bracing for a few more months of hard times. It deserves a little special attention.
Unlike the average consumer who buys passenger tires, truckers don't go to a tire store to pick out tires or select fancy wheels. They look at tires and wheels for their revenue-generating vehicles much differently than that 19-year-old down the street who is working on making his “monster truck” look cool.
The No. 1 thing on that kid's mind is: “How can I make this truck look so 'rad' that Tiffany will think I'm hot?!”
But what are the questions on truck operators' minds? What are some of their burning issues when it comes to tires and wheels? To get a better insight on your commercial tire customers, perhaps you'd like to read some of the questions they have asked me and the answers I've given them. Who knows, perhaps you've gotten these same questions put to you or will in the near future.
Dear Peggy,
I discovered a piece of moderate- sized metal in the tread of a drive tire (not a large bolt; more like a nail or small bolt).
It's not convenient to go straight to a tire shop for a (possible) repair right now. Can I run it this way (possibly for as much as a day) as long as it's holding (proper) pressure, or would that do damage to the tire that would exceed the inconvenience of removing the metal immediately?
I know that if it did puncture the casing, I would have to have it repaired RIGHT NOW (and maybe miss a pickup or delivery). In essence, does the average piece of metal in a tire tread cause enough damage to the tire when running that it is imperative to remove it immediately or can you run it for a while?
—Punctured
Dear Punctured,
As long as the tire is holding ample air pressure, it's OK to run it until you can have the bolt or piece of metal removed. It may be that the bolt is just stuck in the belts and has not penetrated the air chamber yet.
However, as you run, it will be pushed deeper into the tire. Check the tire with a gauge frequently to ensure that you are not losing air. If the tire loses a lot of air and the bolt is long, it can damage the tire inner liner and ruin the tire. If you run the tire low on air, you will run the tire in an overloaded/underinflated condition, which will also ruin the tire.
Get help, though, as soon as you can for this tire.
Dear Peggy,
I am very big on retreaded tires. Recently, I took some 11R22.5 casings to my tire dealer to have them retreaded. These casings happened to be from my trailer that is equipped with tire pressure equalizers.
I was told that since these casings came from a long-haul operation, I could expect to retread them only once. Is this typical? I was under the impression when I first started using retreads that if the casings are taken care of, I could retread them three or four times. Was I mistaken?
—Taken Aback
Dear Taken,
RUN! Do not walk. Run away from that tire dealer! Find a reputable and knowledgeable one immediately. What he told you is absolute trash.
Line haul tires produce the best casings for retreaded tires because they don't see much abuse like cutting, snagging and curbing that you can get in local delivery operation or cutting, chipping and stone drilling that you readily find in on-off road operations.
Over-the-road tires are usually clean—although they may get an occasional puncture—and if the air pressures are well maintained should easily produce at least two retreads. Three or four is not unheard of, although it is not the norm. Since you have maintained the air pressures well on these tires with the equalizers, these tires should provide you with many more lives and miles.
Dear Peggy,
Is there an industry or government standard for powder coating or painting steel wheels for commercial vehicles?
At present I have refurbished, powder-coated wheels on which the finish is migrating out from under compression areas. This has re-sulted in loose wheels. This does not happen on new wheels.
Is this a good process for refinishing wheels?
—Seeing Red
Dear Red,
There is no government standard on refinishing wheels for commercial vehicles. However, there are industry standards that address this issue. Below is an excerpt from the Technology and Maintenance Council's (TMC) User's Guide to Wheels and Rims, which sets the guidelines for the industry:
“Wheel Refinishing: Painting”
“The specific type of paint used is not critical, but the finished paint thickness and curing time are.
“Total thickness of the dried paint coating on each side of the wheel mounting face must not exceed 3 mils (.003 inch). This limit applies regardless of the type of paint used. Excessive paint on these surfaces can lead to loose fasteners, premature wear or wheel loss as a result of the joint settling in.
“For air-dry paints, the typical time required for complete curing of the material is three days. Baking the painted wheel will speed up curing time. Cure temperatures recommended by the paint manufacturer should be used. Undercured paint will have the same effect as excessive paint thickness, since the soft coating will be squeezed from the mounting surfaces and from under the wheel fasteners when they are tightened.”
You stated that the finish is migrating out from under the compression areas. Several things can cause this: If the finish has a tendency to break up, the powder coat was applied too thick or was undercured. If the finish is soft and squishing out, the cause was too much heat during cure. If the finish is peeling or breaking off the wheel, the wheel was dirty and still had oil or other material on it before it was powder coated.
Dear Peggy,
I had a problem with studs breaking on the front axle of a 1988 Volvo conventional I owned.
After racking my brain trying everything I could think of to figure out the cause, I finally removed the wheel balancers that bolted onto the outside of the wheel and the problem went away. I had been running them for quite some time before I began having chronic problems with breaking studs.
Why did I suddenly have a problem after all that time?
—Knocked Off Balance
Dear Off Balance,
Mechanical balancers can affect wheel studs. If you were using a balancer that uses the lug nuts to bolt it on the wheel, you introduced another variable into the fastening assembly.
Something allowed the joint to settle or affected the flatness of the mounting surface around the bolt holes. Burrs on the balancer could have been present, which wore off while you rode down the road. Once gone, these would have left the nuts loose that resulted in the studs breaking. Keep in mind that loose means the nuts had less than 450-500 foot pounds of torque on them and not that they are so loose that you can turn them by hand.
If the metal on the balancer around the stud holes was worn and irregular, the mounting face was no longer flat. This would prevent the attaching assembly from attaining the proper clamp load also.
Since your balancers were older, this may have been the case in your situation. The moral of the story is, check all the components of the wheel attachment assembly—wheels, hubs, drums, nuts and balancers—if they are a part of it during a tire change. If any part is worn, cracked or no longer flat at the mounting surface, it should be replaced or repaired, if possible.
Dear Peggy,
I run Mack tractors and pull 36-foot dump trailers. I run 11R22.5 rib tires that seem to wear evenly.
I am loaded all the time with 75,000-80,000 pounds and drive 80 percent of the time on the highway at 65 mph. I run 105 psi in all my tires, but according to the tire load and inflation charts I should only be running about 70 psi.
If I lower the air pressure to 70 psi, I'm sure I'd get a smoother ride. But would it affect my tire wear? Also, would it affect my fuel mileage?
—Pressured
Dear Pressured,
You definitely need 105 psi in your steer tires in order to carry 12,000 pounds on your front axle. Do not change this pressure.
You can reduce the inflation pressure in your drive and trailer tires, since you are carrying only 4,250 pounds on each tire if you are hauling 34,000 pounds on each tandem. However, there are many drawbacks to reducing inflation pressure to 70 psi.
First, you have no margin for error. It is wise to overinflate a little to ensure that if you lose a little air you still have enough to carry the load. If you run underinflated, you'll ruin your tires. So giving yourself a little extra air pressure is wise.
Second, your rolling resistance will increase dramatically at this inflation pressure and you will see an increase in fuel consumption. A general rule of thumb is that for every 10 psi of pressure loss, a 1-percent drop in miles-per-gallon will result. So you could expect to see a 3-percent loss in fuel economy from the 105 psi you are currently running.
Third, you may find that your tread mileage may also be reduced—perhaps by as much as 12 to 16 percent. Since the tread rubber will be running hotter, the tire also will become more vulnerable to penetration.
All of these things lead to increased down time and higher tire costs. However, you will have a much cushier ride to make up for all of these increased costs.
I would recommend that you maintain your air pressure on your drive and trailer tires in the 95-105 psi range. If it is easier for you to keep 105 psi in all of your tires, then do that.
As you can see, all of these truckers were concerned about getting the best performance from their tires and wheels and reducing their operating costs. Alas, not one was interested in impressing a girl.
Peggy Fisher is president of Fleet tire Consulting in Rochester Hills Mich.