I have 70s on my truck now, I am going to put on a 75, which is a bit taller, is it enough to affect gas milage and/or speedo difference?
Craig

 

Elaborate on what a "bit" is by listing each tire size or the overall height difference, otherwise your responses may be...it changes a little "bit".

 

the lower the number, the wider the tire 75/70/60 ect, add the diameter, 235, 255, 265 ect, the higher the number, the taller the tire your missing the fall tire size, to simply say 70 or 75 means nothing......example lt 265/70 17.......I'm gussing you have 16 inch rims, so a lt265 70/16 is a starting point for you.

 

The truck has 265/70/16 right now, I have a set 265/75/16 ready to install. If a lower # means a taller tire then the new 75s would not be as tall as my 70s right?, However, sitting them side by side the 75 series is taller than my 70 series, how can that be? doesnt the 265 # notate the width? and the 70 or 75 notate the height? Clear this up for me please.
Craig

 

Take a look at Tirerack's Tech pages to understand tire sizes.

265 is the width of the tire in millimeters. 70 or 75 in this case is the percentage of rubber height to section width. If the width is constant (i.e. 265) then 75 will be taller than 70.

If you are lazy, use this calculator. About 3.5% larger between those two sizes so that's how far off your speedo and odo will be. Will it affect fuel mileage and performance? Some people would notice, but most won't.

 

APT is right.

 

APT
your explaination was great, I understand now. Thanks to all who responded
Craig

"265 is the width of the tire in millimeters. 70 or 75 in this case is the percentage of rubber height to section width. If the width is constant (i.e. 265) then 75 will be taller than 70."