1. INTRODUCTION
The purpose of this experiment is to find the coefficient of rolling resistance.
2. TECHNICAL DETAILS
Prior to starting the experiment, the tires were inflated to the tire manufactures recommendation.
The car used in the experiment has two different brands of tires: Fisk Classic on the front and
Kumho on the rear. The front tires were gauged at 35 PSI on the left and 36 PSI on the right. The
rear tires were gauged at 44 PSI on both the left and right. According to The Auto Channel (1),
the curb weight of this car is 1023 lb. The track length is approximately 30 ft of level concrete,
Figure 2.1.
Figure 2.1 – Car and Track
1
The vehicle is pushed to a constant speed and the results measured. The expected result of this
experiment is that it will require very little force to move at a constant speed which will equate to
a low coefficient of rolling resistance.
3. RESULTS AND DISCUSSIONS
The experiment began at 1135 and ended at 1150. The vehicle was pushed forward, the force
reading taken, and then the vehicle stopped. The vehicle was then pushed backwards, the force
reading taken, and then the vehicle stopped. This procedure was repeated four times and the
readings are indicated in Table 3.1.
Table 3.1 – Force Reading
Forward (lb) 15 13 15 14.5
Final Average (lb)
Backward (lb) 12 14 14 14.5
Average (lb) 13.5 13.5 14.5 14.5 14
The average force required to move the vehicle is 14.0 lb. The formula coefficient of rolling
resistance is:
Cr = F/W (3.1)
Therefore the coefficient of rolling resistance is 14lb / 1023lb which is 0.013685 or 1.37%.
4. CONCLUSIONS AND RECOMMENDATIONS
The coefficient of rolling resistance was as predicted, very low. While not part of the experiment,
gas mileage data has been kept for over a year and tire pressure has proven to cause lower gas
mileage. This is due to the amount of work required to rotate the tire. When the tire is below the
recommended pressure, the sidewalls flex and the tire becomes flat on the bottom. The force
required to overcome this flat surface is much greater then a round surface. Better testing could
be completed by using a pull gauge attached to the vehicle and pulled by a mechanical device at
a constant speed over a longer distance; however, no further testing is needed.
5. APPENDIX
Average 1 = (15 lb + 12 lb) / 2 = 13.5 lb
Average 2 = (13 lb + 14 lb) / 2 = 13.5 lb
Average 3 = (15 lb + 14 lb) / 2 = 14.5 lb
Average 4 = (14.5 lb + 14.5 lb) / 2 = 14.5 lb
Final Average = (13.5 lb + 13.5 lb + 14.5 lb + 14.5 lb) / 2 = 14 lb
2
6. REFERENCES
1. The Auto Channel,
http://db.theautochannel.com/db/HyundaiReviews/rankbyspecs_details.php?titleid=1
24103&model=Accent
3