Why did Ford recommended tire size change in 2006?

[engine]

My 2002 4.0 4wd auto has 245 75 16 on the door frame (and on the truck) . This is a 30.5 in tire.

In 2006, for the same truck, the recommendation is 255 70 16. This is a 30.1 in tire.

Why would Ford specify a wider tire (more air resistance) but smaller (slightly more rpms) for the "same" truck?

 

[Denisefwd93]

Maybe their supplier of speedometer gears had an overrun?

 

[adsm08]

Maybe their supplier of speedometer gears had an overrun?

No speedo gear after 98.

They may have found a different size worked better. It may also be that different packages came with different sizes, and you just have two with different sizes.

Sometimes a larger tire is an option.

 

[JohnnyO]

My suspicion was always that they just wanted to run the same size tire as the Explorer and Sport Trac were using. Economies of scale.

 

[Dirtman]

Someone was drunk when ordering tires? They found the new size for 4 cents cheaper? They had a warehouse full of the wider tires going bad in some warehouse? They got bored? Why do auto manufacturers constantly change all sorts of random crap that's been working fine for years? Trying to understand the thought process of the automotive industry will just give you brain tumors.

 

[rusty ol ranger]

Trying to understand the thought process of the automotive industry will just give you brain tumors.

Truer words have never been spoken.

 

[Ranger850]

that's only 2/5 " difference in height, so it could be ride quality or MPG, or like they said, to save a few pennies