Hello everyone, I upgraded my wheels and tires to 20 inch from 18's. I found a set of wheels and tires that were actually lower in weight than the factory 18's to hopefully keep the good gas mileage. I took my truck to my Ford dealer and the said they could not calibrate the Speedo. The tires I had installed were 275/55/20's. They actually told me that the Hypertech programmer was the only way to calibrate the Speedo. Does this sound right?

 

Those are stock tires for a platinum, so I sure hope they can calibrate them.

edit - according to this, however, they can't...

http://www.f150forum.com/f118/2015-s...e-ford-302778/

Seems strange that they can't even switch among their own stock sizes.

 

I am not sure if that tire size is the stock size for the 20 inch rims, but if it is, then you shouldn't have to re calibrate your speedo. The 18s and the 20s should be really close, if not exactly the same size in OD (overall Diameter). The only difference is that you are giving up sidewall height on the 20's and ride quality. The more sidewall you have in a tire, the better the ride, because more sidewall gives the tire more flexability. So what the OE's do is give you a 17, 18, and 20 inch option, but when you look at the OD's on the tires, they are pretty darn close. Just more or less aluminum. Now, there is a difference if you go from a 2wd to a 4wd model, but if stay with stock wheels and tires from say a 4wd to another 4wd the above should apply.
Good Luck.

 

Any time I am looking for tires, I use this little tool to get the tire sizes close to original. Like when I went from my stock 235/75/17 to 18 inch fx4 wheels

On my 2015, it came with 245/70/17, whenever I need to replace them, I will get 255/65/17 which is close, or maybe 20's, but I will use the calculator to determine the size so the speedo is right...