Has it been hot where you are? Recently it was 101 F where I live in sunny Rochester Hills, Mich., with humidity at 96 percent-and let me tell you, it was not a dry heat!
Can you imagine how hot that is? So hot that pigs complained about sweating like fat humans! So hot, chickens were laying hard-boiled eggs! It was so hot, people were pouring coffee in their laps at McDonald's just to cool off.
We're not used to this kind of weather up here in the North. Michigan is a long way from places like Houston and Miami. But it makes me wonder. If I'm melting into my shorts, what are truck tires doing out there on heat-baked roads? Why, they're working hard, ``bringing good stuff.'' If they're unlucky, they're probably running hot, reverting and coming apart at the seams, the belt package or the sidewalls, as the case may be.
That means newspapers will be filled with ``Letters to the Editor'' demanding that retreaded tires be outlawed. Harvey Brodsky, managing director of the Tire Retread Information Bureau (TRIB), will be called to the rescue and will declare that tires fail and come apart because of improper tire maintenance. The primary culprits: underinflation, overloading and mismatching of dual tires. And he will be right.
But Harvey also recognizes that too many ``junk retreads,'' as he calls them, are still being produced. In fact, 5 percent of the tire debris on our nation's roads is attributable to poor quality retreads, and 9 percent of the failures are triggered by botched repairs, according to surveys conducted by the American Trucking Associations' Technology & Maintenance Council (TMC). The primary cause of these retread and repair failures is poor workmanship.
Retread failures cost everyone money. Retreaders have to pay the truck tire owner an adjustment, which wipes out any profit made on the retread sale-in addition to the loss of good will and maybe even a customer.
The trucker loses what could have been a good casing that may have been retreaded a second time if it had been retreaded correctly the first time. He also incurs the cost of additional labor to change his tire, the purchase of a replacement tire and perhaps the cost of a road call.
You may wonder, ``What types of retread failures are occurring out there?'' In the TMC's ``Tire Debris Study,'' retread failures included:
* Bond line porosity;
* Missed punctures;
* Tread separations; and
* Tread chunking caused by poor repairs or bad skives.
Many of these failures could be considered plant failures, but they weren't caught before they were delivered to the customer. All of them could have been avoided if a little more attention to detail was paid to these tires as they made their way through the retreading process.
How many quality inspectors do you have in your retread shop? Well, how many employees do you have in your plant? That is the number of quality inspectors you have. Perhaps they just don't know it yet.
Obviously the more pairs of eyes that inspect a tire, the more likely mistakes will be found. And mistakes can be made at every step in the retreading process.
Industry professionals acknowledge that the initial inspector's job may be the most critical in producing retreads since this person determines whether the casing will establish a good foundation for the new tread. I'm sure your inspector is doing his best, but he or she needs the tools and equipment to do the job right.
Initial inspectors have to be well trained. They need well-lighted work stations and must be well equipped to find problems with tires so that these problems can be corrected or the tires can be rejected. Today, there are so many types of non-destructive inspection machines that can detect all kinds of anomalies, it's easy to degrade the manual initial inspection to simply recording the tire information and entering the casing into the manufacturing process.
But this is wrong! Nothing has yet been developed that takes the place of a trained set of good eyes in the initial inspection stage.
What kinds of mistakes happen in inspection? Well, even though most retread plants now have non-destructive testing (NDT) machines, missed punctures are still a problem, although to a much lesser extent than they used to be. Missed separations are another mistake.
Unless you have a shearography machine, only a good inspector with a discerning eye will catch belt, bead, liner or sidewall separations that appear as cracks, bumps or bulges in the tire.
Potential zipper ruptures are a third problem that has been known to get through initial inspection. Unless you have an X-ray machine or a high-pressure tester and enjoy scaring the heck out of everybody in the plant when a tire blows, your inspector needs to take the time to scrutinize tire sidewalls closely using his or her eyes and hands as well as ears. An inspector must be able to discriminate between a bulge that is a heavy splice or a spread cord-both serviceable conditions-from a problem that is an imminent tire failure.
The buffer operator also has the responsibility of inspecting the tire. While the tire is inflated on the buffer, this person can check for leaks in the casing and bulges in the sidewall that may be evidence of separations or zipper ruptures.
To perform his job properly, the buffer has to do more than mount the tire on the machine and press a button to start things going. Since proper buffing is vital to ensuring a casing is prepared correctly for the tread to properly bond to it, correct buff specifications must be selected and used. With automatic buffers in wide use in plants today, most of the operator error has been taken out of the process, but mistakes can still occur.
The buffer has to be kept in alignment and well maintained to do the job right. The rasp has to be kept sharp to achieve the proper texture without scorching the tire, which will reduce tread adhesion. If the shoulder buff is improper, tread edge lifting will result. For retreads built with wings, lack of shoulder buff or improper crown radius can cause the wings to lift.
The skive station is, I think, the place where more errors happen than any other.
That may be because the newest employee in the plant usually is put in the skive station.
Common problems here are that rubber gets scorched, loose wires are not cut back into the rubber and the entire injury does not get removed.
Too much cement can be applied to the skive, which fails to dry before the tire is built.
Any of these problems result in lack of adhesion and trapped air between the skive fill rubber and the casing-ending up causing a tread separation.