Maintenance Q&A – November 2021
EDITOR’S NOTE: Our dear friend and colleague Paul Abelson passed away on Oct. 7, 2021. While we mourn his death, it is our honor to celebrate his life and legacy in the upcoming December/January issue of Land Line.
Q: I heard on late night trucker’s radio that you should always keep tires inflated to the pressure shown on the sidewall of the tire. You wrote in a number of articles that we should inflate tires according to the load they carry. My driving instructor at community college told us to keep all tires at 100 psi. That means I should keep my tires at 100 psi, or maybe 130 psi, or maybe 75 to 80 psi. I’m confused. Who is right? What should I do and why?
A: How could you even ask? Of course, I am right! LOL. Seriously, there’s a great deal of confusion about tire inflation pressures. I’m surprised that a national tire service chain would provide this misinformation on national radio, but perhaps I shouldn’t be. When I was with Espar Heaters, now Eberspaecher, I faced a similar situation. People from our ad agency, skilled in motivational copy writing, tried writing ad copy for us. They did not know the product or its application, and we always had to rewrite their efforts. My guess is that the tire chain hired an ad agency to write their scripts, and the agency did a little research but not enough.
The pressure molded into the sidewall is the maximum pressure the tire can withstand before you risk having the tire burst. It is not the recommended operating pressure.
Your instructor is probably old-school, repeating the traditional 100 psi recommendation. It may have been valid with the old bias-ply tires (mounted on 22 vs. 22.5 wheels or 24 vs. 24.5) but it is not valid today. Tires are carefully engineered structures, made with dozens of different materials in their sidewalls, shoulders, treads and the underlying structural elements that give each tire its engineered shape. But it is still the air inside the tire that supports the truck. Air pressure must vary as the load on them varies in order to maintain the tire’s desired shape.
Too much weight for the air in the tire or too little air for the weight and the tire will have a lower profile and longer footprint than designed. It will wear unevenly, mostly at the edges. Conversely, with too little load for the air pressure or too much air for the load, the tire’s profile will be too round and the contact patch too short and narrow. Wear will be excessive at the tread’s center.
Today’s radial steer tires probably require 105 to 110 psi to support their 6,000- to 6,500-pound load on each tire. Drive and trailer tires may need only 80 psi or less for a full load with 4,250 pounds on each tire. When partially loaded or empty, even less pressure will be needed. Wide-based singles, 445/50R22.5, require higher pressures to carry 8,500 pounds per tire.
Again, check the load-inflation tables for your particular load.
Tire manufacturers spend a great deal of time and money on research to determine the proper inflation pressure for each tire and for each load. It is they, not I, who publish the load-inflation tables that are available from your tire dealer or on your tire manufacturer’s internet pages
Q: Just this past April I did my summer prep on my 2017 Freightliner. It included putting in four new 650 CCA batteries. The old ones were the original ones that came with the truck. When the cold weather hit this fall, I had trouble cranking the truck. Finally, it wouldn’t start at all when we had our first freeze. How could this happen with a new set of batteries? Can I get my money back from the dealer?
A: I can’t answer about getting your money back. That’s between you and your dealer. You may get a credit toward the replacements you’ll surely need. But I can shed some light on why your batteries failed. Even though the problem showed up as a failed cold start, it can possibly be traced to summer heat. Automotive lead-acid batteries lose more than half their capacity to accept a charge for every 15 degrees F above about 80 F, the temperature at which batteries are rated.
So at 110 F, they can diminish by half and half again, or up to 75%.
While auto batteries live underhood, where summer temperatures can easily exceed 140 F, truck batteries close to hot summer pavements can experience periodic temperatures above 110 F, enough to permanently damage them over three months of summer.
Your batteries will definitely need replacement, but you should also go over your entire charging system. First of all, keep your batteries as cool as possible. In summer, try not to park over hot pavement during the hottest daylight hours. Regularly check all cable connections and the batteries’ surfaces for any signs of corrosion or dirt buildup. Even dirt can act as a conductor to drain batteries. Corrosion weakens contacts, lessening cables’ ability to transfer current. Make sure the alternator belt is in good condition and that the tensioner is operating properly so you get all the current your alternator can produce.
Make sure accessories, fans, radios and lights are all off when not needed to minimize current drain. Spec the best batteries for the job that you can afford, installing high CCA (cold cranking amp) batteries to provide a margin of safety. Consider AGM (adsorbed glass mat) premium batteries. The batteries will still eventually wear out, but you’ll extend their life by a year or two. LL