Hey guys, got new tires on the truck and I input the exact size (34.64) into the programmer and my speedometer reads 2mph fast (70 on the speedo is acutally 67.5-68mph by GPS). Without playing a trial and error game, does anyone know off hand what size bigger tire I need to put in to get that close?

Thanks in advance!

 

What programmer are you using to calibrate your speedometer?

 

And, is there a programmer that accepts Revs Per Mile as a component for calibration (for lack of a better way of putting it)? I have no experience with programmers, but I've been aware of their existence since 2004 when I discovered the automotive innernets!

 

I didn't have time to even check this thread, but thank you for the replies. The cooper STT Pro's were in a 35x12.50.20. I used an SCT X4. the correct tire size that put me right on by GPS was 33.8 inches. For anyones future reference!

 

I'm getting new wheels and tires installed today......do you rent that sucker out???

 

It's not something you can borrow out. It's a programmer locked to my truck with the tune i'm running. You can buy a designated tire calibrator for like $200, but for that you mine as well double down and get a programer with custom tunes to go with it.

 

I had to call my dealer AGAIN for service on our 2017 Fusion. While on the phone I asked if they are able to recalibrate my 2017 XLT due to my bigger (taller) tires. He had to check and call me back.....


His response was "No, it is not possible to recalibrate your 2017 for different sized tires."