tire sizes
 

I'm going to be needing a new set of tires soon. The OEM size is 255 / 65 - 17. It seems that other models of F-150s have 255 / 70 or 255 / 75 tires on the 17 x 7.5" rims. I've got a few questions:

1) Would that increase in size improve my fuel economy? If so, by how much?
2) Would that affect handling, and if so, how?
3) Would that affect load capacity, and if so, how?

Load is probably most important, followed by economy.

If I'm doing my math right, my current tires have a circumference of 96", while the 75's would have a circumference of 101", which would mean 659 revolutions / mile vs. 625, which would mean the engine would turn over ~100 RPM lower on the highway. I think that would help some, but how much? And I won't do it if it's going to destroy my ability to haul a load or take a corner. Not that the truck corners worth a darn anyway...

And how would I get the spedometer reset?

Thanks,

Scanguage would probably reset the speedo for you. I can't tell you about the fuel economy, that varies form tire to tire and driving habits. As a general rule though, taller is better.

As long as the load rating is up to what you are hauling go for it.
 

I have taller tires on my truck and it runs LOW rpm on the road.

Dug around and found the Scanguage info - thanks.
I'll give it a shot once I'm down to threads on my current set.