The effect of tyre pressure on vehicle performance

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In the world today, due to the high cost of running a vehicle, there has been many research to see ways of minimizing this cost. Some of these cost come from the tyre of the vehicle, amount of fuel needed to run the vehicle smoothly, buying spare parts of vehicles and ensuring safety of the vehicle. This thesis seeks to find the effect that tyre pressures of vehicles have on the fuel consumption and the various ways of reducing this effect if there are any. First of all, a survey of vehicles on KNUST campus was done to ascertain how tyre pressures of these vehicles deviate from the recommended tyre pressures. Then the survey was extended to other four places namely, Kumasi Polytechnic campus, Asafo, Roman Hill and Kejetia. The survey showed that most of the vehicles tyre pressures deviate from the recommended tyre pressure. Out of 660 vehicles surveyed in these five areas in the Kumasi Metropolis, 96.52% had their tyre pressures deviated from the recommended tyre pressures. That means only 3.48% of these vehicles had their measured tyre pressures conforming to the recommended tyre pressures. From this result obtained, a case study was carried out to find out whether these deviations in the tyre pressure of the vehicles have effect on the fuel consumed by the vehicles. Five Nissan shuttle buses in KNUST campus with Vehicles 1, 2, 3, 4 and 5 were studied. A three month case study was carried out starting from September 2009 to November 2009. Values were taken each day at an interval of three hours, that is, 8:00, 11:00, 14:00 and 17:00. In each reading, values were taken for distance travelled, fuel consumed and tyre pressure for all the tyres of the vehicles. From the case study, it was observed that, there is direct effect of the vehicles tyre pressure on the fuel consumed. It was seen that when vehicles tyre pressure deviate from the recommended tyre pressure, there is additional fuel consumed by the vehicle. Using Vehicle 1 as an example, with ten percent tyre pressure deviation above the recommended tyre pressure, an additional fuel of 2.72 litres will be incurred for Kumasi/Accra return trip (540km). Similarly, 10.87 litres and 24.46 litres of an additional fuel will be incurred for twenty percent and thirty percent tyre pressure deviation below the recommended tyre pressure for Kumasi/Accra return trip. These will result in additional money spent by the drivers. In all it was seen from the research that any deviation in tyre pressure of vehicles result in an additional fuel consumed by the vehicles. Also, most vehicles in the Kumasi Metropolis have their tyre pressures deviating from the recommended tyre pressures.
A thesis submitted to the Department of Mechanical Engineering Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering