Went from stock 255/70/16 to 265/75/16. Spedo is obviously wrong. I'v had these bigger tires for 55k miles and I'm putting on new ones of the same size. Is there some product that I can install to calibrate the spedo to tell me the actual speed I'm going? From what I'v calculated I got a free 8-9k miles over the couple of years with the bigger tires. I'm not upset about that at all... but I'm never going to trade in the truck, so I don't care if the miles add up at the normal rate.

 

Truspeed from superlift should do the job. Most tuners will also get you close.

 

Checked out the product... thank you, exactly what I was looking for, but at the same time, dumb product. $200 for an item that does one thing, I might as well save another hundred or so dollars, and just get a superchip, and program the computer with the new tire size, while getting better performance with timing upgrades and other stuff... but still, thanks for the reply.

 

I would hate to tell you this but there is a speedo gear itself in the tailshaft of the tranny on the drivers side to give you your speed. I bought a superchips tuner and it showed nothing for correcting the speedo. I suggest go to 4x4 shop or dealership and get the correct number tooth speedo gear. I posted a few months ago in the 97-03 F150 forum, and you would need a 19 tooth speedo gear to get an accurate spedometer reading.

 

With the tuners you MUST enter your gear ratio and tire size. Leaving either stock will not correct the speedo. I learned this from personal experience, with superchips, hypertech and sniper.