Heavy Duty Trucking, September 2019

tread wear The types of irregular wear include alternate lug wear diagonal wear multiple flat spotting and erratic or inner rib depression wear Thats because whether youre dealing with a pressure differential or a height problem its the smaller tire in the set that bears the brunt of the damage Two tires paired together on a dual assembly must have the same circumference or height or diameter in order to cover the same distance as they roll along If the diameter or circumference of the two tires are even slightly different the smaller of the two tires will scrub along the pavement trying to make up the distance traveled by the larger tire Its that scrubbing that kills tread life But the larger often newer tire doesnt get off scot free either Because of the smaller tires limited footprint the larger tire has to carry a greater share of weight This causes additional wear to the tread face of that tire and greater stress on its sidewalls So the smaller tire in a mismatched set of duals is being scrubbed to death while the larger tires lifespan is being shortened because of overloading the sidewall For those reasons fleet consultant Darry Stuart owner of DWS Fleet Services says TMC recommends keeping dual tires within of an inch in height in order to minimize scrubbing and ensure the tires work together on the road Im not as stringent on that spec as most people he admits Most people like a closer spec on the tire height But Im being honest about the labor costs required to match those tires up away from home Are you willing to pay 150 to swap a tire out over an extra quarter of an inch when that truck is away from your shop When looking at pressure differences Coopers Mosier notes it is not uncommon to find dual tires with different inflation pressures but it is far less common in fleets using automatic tire inflation systems More and more fleets are investing in such systems because they realize the importance of maintaining proper inflation pressures he says Industry wide it is acceptable for dual assembly inflation pressures to be within 5 psi of each other A recent study at three different trucking companies revealed 79 of the dual assemblies fell in the zero to 5 psi range 16 were between 6 and 10 psi difference and the remaining 5 measured at a 11 psi or greater difference To put the 5 psi difference in tire pressure into perspective the lowest inflation tire will have a circumference that is 5 16 inches smaller During every rotation cycle the smaller circumference tire must scuff ahead to keep up with the tire with more inflation just like two tires with mismatched diameters will do Bryan Golden vice president of fleet maintenance for Southeast Logistics in Tuscaloosa Alabama says mismatched diameter tires are the bigger problem for his vehicles Golden has a reputation as something of a perfectionist and says he prefers to keep his SEPTEMBER 2019 HDT 83 WWW TRUCKINGINFO COM Weve got your back so you can weigh pay and get going 1 877 CAT SCALE 228 7225 catscale com weighmytruck comNow accepting WEIGH PAY GET GOING You know you can trust CAT Scale for guaranteed accurateweights You can get that same guarantee even faster byusing the Weigh My Truck app Weigh and pay all from your mobile device without leaving your cab WeighFaster CAT HDT 081219 qxp_ Layout 1 8 12 19 10 51 AM Page 1