has anyone had the dealer change their tire size for them? say from 34 (stock) to 35 or such?

 

I tried, if that counts.
I'm unsure of the exact options but the tech I worked with tried available 18 inch rim sizes.
All except factory for 3.31 ratio and 18 inch rims threw a CEL.
In addition any 20 inch rim size threw a CEL because you can't buy 20 inch rims with a 3.31 ratio.

My dealer told me if I could find out the exact setting that works to bring it back and they'll change it for me but we gave up for now.

 

btw i have the 20" option (275 65 20's) and 3.55 axle

 

Are you asking for the speedo? I ran a 325/60/R20 duratrac for winter and my speedo was bang on. Checked it with a portable gps. Thinking they must read a little slow with stock tires.

 

Did you use that size tire on the stock 20" wheels? No lift or spacer?

 

Computer won't accept any tire size larger than 34" w/o throwing a CEL. Makes absolutely no sense at all but that's how it is. Falls in the same stupid category as the TPMS adjustment issues. Not sure wtf Ford was thinking, or wasn't thinking....

 

so andrew, what size tires do you have with that lift. i know youve put pics up before, but could you throw a few up in here too? im lookin at 295 65 20 trails, on a 4 inch lift. wonder what kind of effects im to expect

 

My speedo was off with stock tires - 275/70R18 (33.2").
I switched out to some larger tires - 285/75R18 (34.8").
My speedo is now spot on with GPS.

If you don't have a portable GPS you can download a free app on your cell/smart phone to check your speed.
It is called "GPS Speedo" on the Android system.

_

 

My tires are 35x12.50 but actually measure just over 34" tall once mounted. My stock tires actually measured about 33" tall and were sized at 34". My tuner will adjust tire size up to 34" which is almost spot on for my 35" tires. My speedo is off about 1 mph (slow)

 

I think the 295 65 20 is just a tad bigger. And the reason im likely going that route is for the size and load rating and psi. Nittos size chart is super useful

 

According to the calculator, 295/65/20 = 35.1" Diameter

 

I ran the 325's on stock 2010 F350 rims that I got on kijiji cheap. I have a 4.5" lift.

 

That is the exact tire option I'm interested in. Nitto Trail Grappler
Please let us know what you chose to do. I don't know if we are forced to buy different wheels (I think you do) and what option you chose. I would like a black wheel preferably with some deep well affect that is made in USA. I am not interested in doing a lift so I'm very curious how you go about it.

 

the nitto 295 65 20 is the biggest 20in tire they have, also with the highest load rating and psi rating. thats the route im goin. may end up putting it on the stock rim tho for now. with a 4 inch lift tho

 

They make a 37" tire.