Speedometer and Tires

[William2002F350]

I am running stock size tires on my truck (according to the door sticker) and my speedometer reads 5 mph faster than what I'm actually doing. I know its actually a percentage that it reads off, but basically 5 mph faster.
My only guess as to why is that a previous owner ran bigger tires and had the speedometer recalculated for those tires
I plan on my next tires going up to 285 or maybe 295 somewhere in there as i think they look good on a stock lift truck, and im hoping that will correct my speedometer.
My buddy runs 285's on his stock PSD and his spedo reads about 5 mph slower than what he is actually running.

[SuperCrutyPS]

Did your truck or does your truck have a programmer capable of adjusting for tire size? If so, maybe it's calibrated for bigger. Just a thought.

Also, use this to play around with tire sizes and what differences they make to the speedo.
Tire size calculator

[William2002F350]

Originally Posted by SuperCrutyPS

Did your truck or does your truck have a programmer capable of adjusting for tire size? If so, maybe it's calibrated for bigger. Just a thought.

Also, use this to play around with tire sizes and what differences they make to the speedo.
Tire size calculator

I wish I did, but i do not, all i have is a bully dog...i know i will prolly get flamed for having that as it is a generic tune
That tire calculator is pretty cool, thanks