My speedometer seems to be off. I have a 2000 sc 4x4 f150 that came with 16" rims, but at some point they were replaced with factory chrome 17" rims of an unknown year. I am thinking that the new wheels are taller than the originals which is causing my problem. Can anyone tell me the exact height of the two tires so I can calculate the percentage difference to determine how far off my speedometer is? It now has the 17" with P265/ 70 R 17 tires.

 

OK, I found a tire size calculater that says the 17 inch tires are 1 inch taller than the 16 inch tires. Who would have thought..lol... It also says my speedometer should be reading around 3.2 mph to slow. I think it is closer to 6-8 mph to slow. Any ideas on what could make it be off by more other than someone changing the gears?

 

I can't give you any definite answer but maybe the computer has been programmed for a different tire size. On my brothers 04 ranger he has to change the tire size in the computer when he puts his bigger tires on. And in any case his speedo seemed to be 3-4 mph off when he bought the truck new in 04 so that could be your issue as well, just compounded with the bigger tire.

 

Thanks, I may see if the ford dealer can change or correct the speedometer.