Tire Size and Speed / Mileage etc.
 

I have a 2002 Eddie Baur Explorer which came with 16 inch 245 SR 70 tires. Its time to replace and I have found a much better deal on a 16 inch 255 SR 70 tires and wonder what the effect would be on speed and if it would affect miles showing on the odometer, thereby affecting true mileage and the times to do regular mainenance? Will it rack up miles quicker with the 255s vs the 245s?

Thanks,
Semosig

I doubt that small of a size increase would make much, if any, difference. You can go to tirerack.com and pull up the each of the tires, click specs to get the diameters for each.

You can download the GEARS.exe program I wrote a while ago, from the site here and it will give you the info you are looking for. You will need to know the final drive ratio (erar end gears) and the ratios for the various trans gears and you can get tire dia, circumference or rotations per mile from the manufaturer's web sites. If your vehicle has an auto trans there will be some error as it was made for a manual trans car (914 actually).

Try playing with this.

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

http://www.sdspeedo.com/

http://forums.pelicanparts.com/uploa...1124850035.jpg

Based on Redbeard's post, I'd say that you would also be getting 0.0005 more miles per gallon :p