Changing Tire Project

BY: Courtney Keyes, Daniel Dickens and Landon Moody

Changing Tires

If your odometer reading is 50,000 (miles), you have actually traveled 56048.5 miles. If your speedometer reading 70, your actual speed is 78.467 miles per hour. If your mile per gallon with factory tires is 17, what is your mile per gallon with the new tires.


First you need to set up a proportion and do 1 over 91.9624 and then X over 103.0880. Once you multiply and divide them out you get the answer 1.12097. With that you multiply it by 50,000 to get 56048.5, for the estimated miles. Next you multiply 1.12097 by 70 and you get 78.467 for your actual speed. Last step you multiply 1.12097 by 17 because that is the MPG with the factory tires. Once you add the new tires, the MPG increases by 2 making it 19.0569.

Information used:

Factory tire size: 225/75/16

Replacement tire: 285/75/16

MPG: 17 city, 21 Highway

Modifications: None