| Heavy Duty Protect casings for retreading By David A. Kolman, Editor Tire cost is a major reason why more than 85 percent of fl eets retread today, say offi cials with Pressure Systems International (www.psitireinfl ation. com), manufacturer of the Meritor Tire Infl ation System by PSI. Retreads are a third to half the cost of a new tire. Because today’s commercial truck tires are designed to be retreaded multiple times, “protecting the investment in your casings is critical to reducing your tire budget and lowering cost per mile,” they note. Tire casings that are taken care of diligently should last a minimum of one retread and often two retreads in linehaul service. Tire casings in pickup and delivery service can expect up to three or four retreads. PRESSURE One of the best ways to maximize the retreadability of tires is to maintain proper tire infl ation pressure because air is what carries the load. PSI offi cials advise referring to published load infl ation tables for the correct “cold” tire infl ation pressure for a fl eet’s worst case load scenario for a given axle and tire to determine the best infl ation pressure. The load infl ation tables are based on a cold temperature of 70 degrees F, they note. Tire pressure will increase about 15 percent after running on the highway at 65 mph and fully loaded. It can take a tire several hours to cool down after coming off the highway. Therefore, “it makes little sense to check air in a ‘hot’ tire, they point out. “The best time to check air pressure is during the morning driver walkaround when it will be the most accurate. Always utilize a calibrated tire pressure gauge when measuring tire pressures.” CHIEF INGREDIENT The major ingredient in commercial truck tires is natural rubber. If a tire is running underinfl ated, “the casing becomes signifi cantly hotter because of a combination of the longer tire footprint – 18 percent more rubber on the road at 80 psi versus 100 psi – and the additional fl exing of the sidewalls will heat up the natural rubber,” explain PSI offi cials. When the steel belt package reaches around 200 degrees F, the natural rubber based compounds inside the tire start will start reverting – decomposing due to excessive heat. This is unnoticeable until the retreader rejects the casing for retreading, they point out, and “can be a major blow to the tire budget.” Tire casings that are well taken care of – by maintaining proper infl ation pressure, protecting them from cuts and stone penetration and not running the tread down too low – can often be retreaded more than once. Photo courtesy of the Retread Tire Association and Bandag Another tip for maximizing retreadability is to protect the casing from cuts and stone penetration by not running the tread down too low. This, PSI offi cials say, will make the casing more susceptible to damage. It has happened By David A. Kolman, Editor Two new diesel engine oils came to market on December 1: CK-4 and FA-4. Formerly known by the oil industry as PC-11 – the 11th upgrade to proposed categories of diesel oil, these two oils are the new quality standard for heavy duty diesel engine oil. They deliver increased resistance to oxidation – an issue in today’s hotter-running engines, as well as improved resistance to aeration and mechanical shear. CK-4 is an updated version of CJ-4. It should be used in all engines where CJ-4 was previously recommended. However, CJ-4 oils can still be used during the transition period, which is expected to run through mid-2017. CK-4 oils are going to be available in 10W-30 and 15W-40 formulations, as well as other traditional viscosity grades. They can be used as the normal fi ll and top-off on older engines. It will be the recommended oil for all Cummins engines using Ultra-Low Sulfur Diesel (ULSD). Fleets currently performing routine oil analysis may notice a change in the oil chemistry, but this is not anticipated to cause any signifi - cant issues with mixing CK-4 and CJ-4 oils. It is best to work with one’s oil supplier to ensure a smooth transition. VISCOSITY FA-4 a new low-viscosity oil that has potential fuel economy benefi ts, but may not be compatible with all engines. FA-4 oils will be offered primarily at the 10W-30 viscosity grade, with some 5W-30 formulations available in the future. The lower dynamic viscosity (how the oil performs at high temperature and shear) leads to thinner oil fi lm thickness and may reduce friction within the engine (which can be signifi cant at certain duty cycles), improving fuel economy. For each on-highway engine, Cummins will make an individual decision on which oil category it recommends and update each owner’s manual accordingly. However, FA-4 oils will not be recommended for off-highway engines. It is advisable to reach out to your local engine distributor for questions concerning these new oils and how they may impact your fl eet maintenance. Sources for this article were the following Cummins personnel: Ryan Denton, Ph.D., technical specialist; Corey Trobaugh, Ph.D., technical specialist; and Nate McLeese, oil drain interval subject matter expert. Cummins (www.cummins.com), a global power leader, is a corporation of complementary business units that design, manufacture, distribute and service diesel and natural gas engines and related technologies, including fuel systems, controls, air handling, fi ltration, emission solutions and electrical power generation systems. 22 FLEET MAINTENANCE ❚ NOVEMBER/DECEMBER 2016 ❚ VehicleServicePros.com
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