The wheel is an important load-bearing and transmission component of a vehicle. The rear wheels are fixed on the rear axle through wheel nuts, allowing the wheels to carry and transmit power according to the posture specified by the rear axle. After a certain light truck was put into the market, frequent feedback indicated that the rear tires were wearing unevenly. In this article, we analyze the cause of the problem and propose optimization measures, providing a reference for solving similar problems.
The light truck uses an integral rear axle, and the wheels are mounted on the rear axle through nuts. After receiving feedback concerning the problem, an investigation was immediately conducted, and it was found that all the vehicles with faults had the same left outer rear wheel wear. Specifically, the left outer tyre and inner tyre showed obvious outer wear. The outer tyre wore more severely than the inner tyre.
According to the characteristics of the stress of the light-duty truck tires, there may be four mechanisms that cause wear:
Poor wear resistance of the tires;
Inadequate load-bearing capacity of the tires;
Poor installation accuracy of the frame and spring, causing the wheel posture to be incorrect;
Poor precision of the rear axle, causing incorrect wheel posture.
When any of the above four situations occur, or when one or more occur simultaneously, tire wear may occur. In the following text, each factor affecting tire wear will be verified one by one, excluding interference factors, and the main cause will be found to implement corresponding improvement measures.
Tested tires of the same manufacturer and specification on a bench and verified that they could meet the wear life of 50,000 kilometers;
The tires underwent multiple road tests on the complete vehicle before the vehicle was released to the market and completely met the wear life of 50,000 kilometers;
All tires are unevenly worn on one side, rather than being completely ineffective;
After replacing the tires on the faulty vehicle with other brands for verification, the uneven wear still existed.
The tires for the vehicle can bear 560 kg, and the total load of the rear axle of the vehicle is 1375 kg. The load rate of a single tire is only 78%, which is much lower than the standard requirement of no more than 90%. Therefore, insufficient load-bearing capacity of the tire can be excluded as a cause of the fault.
By scanning the mounting points of the frame and spring of one of the faulty vehicles, it was found that all mounting points were qualified, so this factor can also be excluded.
According to the above analysis, we optimized and redesigned the welding fixture of the half-shaft sleeve and bridge shell body of the rear axle and made corresponding improvements to the product drawings. The specific improvement measures are as follows:
The bolt-fixed welding fixture was changed into an integrated welding fixture to eliminate the looseness of the fixture and ensure consistent welding quality;
Taking into account the requirements of mechanical processing, welding accuracy and the use of light-duty truck tires, the assembly drawing of the rear axle was revised to clearly specify the inspection requirements of the wheel installation end face: the angle between the one side and the center line of the rear axle should be no more than 15 degrees, and the angle between the two sides should be no more than 25 degrees.
Three new rear axles were produced using the optimized and improved welding fixtures, and the wheel installation end face was scanned and tested during the road test. The result showed:
The scanning tests of the wheel installation end faces of the three rear axles showed that all the angles on the wheels met the requirements;
Three rear axles that passed the inspection were installed on severely faulty vehicles for verification, and after nearly three months of follow-up, there was no longer any uneven tire wear on the rear wheels.
Through the above analysis, we can draw the following conclusions:
The main cause of the uneven lightweight truck tires wear is the looseness of the bridge shell welding fixture, which causes a large front toe angle on the wheel installation end face and causes a large front toe angle between the rear wheels;
The optimization and improvement were effective, confirmed by scanning tests and road tests;
The requirements for the distance and angle of the wheel installation end face on the rear axle were added, reducing the risk of uneven tire wear caused by the incorrect posture of the light truck's wheels from the component level.