I will be going from the stock 255/70-16 tires to 265/75-16 and would like to know if I can recalibrate the speedo myself, or do I need to take it to a dealer?

I appreciate any help.

 

Are you sure about your sizes? The stock tire size on my '01 2x4 SuperCrew was 255/75R16, which is pretty common across the board for F150's. If that's the correct stock size, then I don't see why you're even worrying about the speedo. By my calculations, you'd only be increasing total rolling diameter by about .5" by running the 265/75R16's, which would translate to a deviation in your speedo of about 1 to 1.5 mph (definitely not a big deal).

My suggestion, put the new treads on and go enjoy your truck!

-Mike-

 

Origingal tires were definitely 255/70-16's. It's a 4x4. Maybe that is the difference is tires from yours.

By my calculation the 265/75-16's would put my speedo off by approx 5 mph at 60.

 

The 4x4 issue might indeed explain the stock tire size difference you mentioned. I had just always taken for granted that the stock treads on 4x4's were larger than those on 2x4's.

Just an opinion, but I myself wouldn't sweat the differential even at 5 mph. I just don't see it as a bigdeal (ha, username used in post). My suggestion, if you want to up the performance on your truck, and have the ability to adjust your speedo yourself, is to purchase the SuperChips MicroTuner. I bought one and installed it's features on my truck. The improvement in performance was very noticable. In addition, the MicroTuner will allow you to adjust your speedo for a change in tire size and/or a change in rearend gearing. At any rate, you could probably buy the MicroTuner for the same or less $$$ that the dealer would ding you to adjust your speedo. Something to think about if you really feel the need to have an accurate speedo.

Good luck.

-Mike-

 

Ford didn't use a 255/75/16 from the factory, they were all 70 series in the 255s. And the 4x2 got the same tire sizes that the 4x4s could get as well. Now the microtuner will NOT be cheaper or as expensive as a dealer would charge to reprogram the computer. Last I saw a microtuner was in the $300 if I'm thinking of the right scanner. Ford doesn't charge anywhere close to that, or if they do the dealership is raping you on it. Now the thing is the microtuner will do more for you than just resize your tires, so its up to you, but its cheaper to have the dealership reprogram the tire size if thats all you want.

 

You are absolutely correct so long as your dealer does not operate like the two dealer service departments I have near me. Both of them are in the business of hyjacking their victims on each visit. A friend of mine visited one of these dealers for a 'front' brake job on an older Explorer. What he ended up with was a $400 bill and major brake shimmy in the nose (dealer didn't even turn his rotors as part of the deal). I am not a huge advocate of using the dealer's service department for anything other than warranty claim work. Since I'm a pretty good mechanic, I don't have to. The MicroTuner I suggested will address the speedo discrepancy issue barnesjb noted, as well as provide a little more go power for the bigger tires he wants to run. And as the old saying goes, you can never have too much power.

-Mike-