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The automotive research and development environment is increasingly challenging and complex, full of new technologies, regulations and customized customer needs. In addition, the cargo transportation market is very dynamic and competitive, becoming complex the strategies for companies in this segment. According to Anfavea (2018), this trend, especially in large urban centers, has driven the intention to use light commercial vehicles to capillize deliveries in destinations with a high demographic concentration and traffic limited to medium and heavy vehicles. In this scenario, the demand for diversified products is increasing in order to overcome the main tradeoff: “minimizing the size of the trucks and maximize the load capacity”. It brings the number of complex projects.

This paper aims to present the difficulties on designing and tuning a tractor suspension, specially due to its particular mass distribution and the trailer influence on its dynamic behavior. It also presents the development of a primary suspension for the new VW 18.310 Tractor. The drivers for the development of this new primary suspension were: improve comfort level; achieve a better condition on fragile load transportation; and allow different fifth wheel positions and heights (to take the most advantages of legal limitations on GAWRs - Gross Axle Weight Rating - composition height and length). This should be accomplished without affecting other vehicle dynamic characteristics such as handling. Due to its benefits to the pavement, the additional facility on tractor-trailer coupling operation and some package limitation, a mixed suspension (parabolic springs on the front axle and pneumatic foils on the rear) is chosen on the cost vs. functional attributes trade off process.

Windup behavior is particularly dangerous in a commercial vehicle, since it can generate undesired lateral movements. Methods previously applied to determine this behavior were not cost nor time efficient. A new proposed method that applies CAD/CAE tools was presented in a previous paper, but that work still relied on a correction factor that is based on a experimental test. Therefore, the present study is geared at eliminating these experimental tests, through the use of a suitable mathematical model and nonlinear analysis.