Tire size change and accuracy of odometer

[bmacsys]

I was just wondering if anybody knew a mathematical formula to know your mileage accurately after you change tire sizes. My sons truck stock had P245 tires and now he moved up to P265. If his trip odometer reads 100 miles what did he actually travel 105 miles???


Thanks

 

[therieldeal]

http://www.miata.net/garage/tirecalc.html

 

[Wicked_Sludge]

http://www.therangerstation.com/tech_library/Speedometer_Change_From_Tires.html