Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Committee Chair/Advisor

Jalili, Nader


There are various losses associated with passenger vehicle that affect its fuel economy as it is being operated. These losses include engine, driveline, aerodynamic and rolling losses. While engine, driveline and aerodynamic losses are inherent with the vehicle due to large number of parts that go into assembling, rolling loss is associated with the vehicle tires and it is the only part of the vehicle that comes in contact with the road. The rolling resistance of inflated tires is an important component of resistance to vehicle motion and contributes to vehicle fuel consumption. Many research works have been focused on how the various tire parameters (e.g., load, inflation pressure and speed) affect rolling resistance so that fuel economy can be increased. Recent studies indicate that inflating tire with nitrogen can maintain proper inflation pressure and decrease the deterioration of the rubber. Therefore, the goal of this research is to explore the probability of using nitrogen inflated tires to improve vehicle safety, performance, and reduce operating cost. In order to accomplish these goals, literature review was done to study the characteristics of tire and methods to improve the vehicle fuel economy and increase tire life. Based on this, a mathematical model was developed and refined to predict the rolling resistance of tires identifying the key parameters affecting them. Considering the possibility of inflating tires with nitrogen, the pressure sustainability of the inflation gas in tires at different operating conditions was tested. However, this does not represent the real driving conditions. Putting to test the tires filled with nitrogen under driving conditions would further help understand tire behavior and how this would affect the tire contact patch area with time. Comparing the test results of nitrogen inflated tires with air inflated ones was performed to determine the importance of nitrogen inflation to cut down the cost spent on fuel and replacement tires. Extensive shop testing was done at MARC (Michelin America Research Corporation) on different passenger car and truck tires. Qleak tests were conducted at room temperature for 16 days, while Sleak tests were performed at higher oven temperatures for about 28 days. It was observed that nitrogen inflation can maintain tire pressure approximately 35% to 55% better than air inflated tires for Qleak tests and about 29% to 35% better for Sleak test depending on tire type. In order to better understand the problem at hand, road testing was also performed on Wal-Mart truck fleet by inflating the tires with both air and nitrogen gases. The results demonstrated that nitrogen inflated tires improve tire life by about 50% and vehicle fuel economy by 23%. Considering these experimental results and extensive computer simulations, it was proven that nitrogen filling in tires help improve tire life and vehicle fuel economy.



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