For anyone who has put larger tires on their truck did you have your speedo, odometer, and gear ratios recalibrated? i am switching from 275/65/18 to 295/70/78. Would ford be able to do this, or a place like firestone or just tires. just tring to figure pit the best place to have the mounting done.

 

WOW, a 78 inch rim! Just kidding - your typo though.

You can use a tuner or Forscan to make the adjustment. I personally like Forscan as it allows you to change a lot of other settings I find useful. Look for a Sticky in the by year section for a Forscan thread

 

I went from 275/65/18's to 35x12.5x17. I bought a Hypertech speedo calibrator from AutoAnything. I don't have a compatible computer for FORSCAN, and all I needed was to calibrate my speedo.

Ford "can't" re-calibrate for you, not sure why.

 

nah i just know it was about 2-3 miles slower then actual speed. stay at 70 or so on the freeway and no issues. i always drive like i got my kids in the truck now days anyways.

 

I tried having the dealership do it for me a couple days ago. I say tried because they told me they could, scheduled me, spent an hour with my truck, then told me they couldn't.

I was just about to start a thread asking if anyone has had success with a dealer doing this. Guess I'll look into forscan.

 

Last I've heard, changing it in Forscan throws a CEL. They may have it figured out now though.

 

Last I heard is Forscan can't do it, I tried on my truck albeit an older version, I also have the same computer hardware/software dealers use and that's a no go as well. The only thing that worked for me is my Sctx4 programmer.
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So do most people just let the speedometer be inaccurate? It doesn't seem like a quick easy and inexpensive fix?

 

Use a Hypertech speedometer calibrator. That's the only way I am currently aware of if you increase the tire height.

 

Will using this device cause any issues such as a CEL?