Okay I stopped being lazy and looked up my diameter and I believe the sock diameter is 27" (anyone correct me if I'm wrong, I'm not stock anymore). If the diameter of your new combo comes to 27" or close (my nitto's are 26.97) then you should be fine. The setting for my tire is 770 revolutions / mile and I just used my sct tuner to adjust accordingly.

 

yes that is correct and you can do the same with diablo

 

They go by the number of revolutions per mile. I forgot what brand are the original ones but I still remember they were 235/55/17. That size continental conti winter contact ts790vtires make 767 rpm. I'm guessing 18 inch ones would be 235/45/18 and those are at 793 rpm (continental conti sport contact 2). The difference is about 3 percent which means if you were doing 103 with the18 inch rims in reality it would be 100mph if you still had a 17 inch rim setting set on the car which is really too little bit of a difference. To answer your question, no, ford does not have a different tunes for the 2 of them. They only adjust that one tire setting just like you would on an SCT calibrator.
P.S. going by the overall diameter is inaccurate when it gets to things like reading the vehicle's speed, that's why the set with revolutions per mile instead. If you need rpm specs on your tires just message me and I'll get them for you. Oh by the way. As your tires wear it affects rpm and also the overall diameter so just from that you'd get a or so percent difference on the speedometer reading on new tires vs the old ones.

 

They got by the number of revolutions per mile. I forgot what brand are the original ones but I still remember they were 235/55/17. That size continental conti winter contact ts790vtires make 767 rpm. I'm guessing 18 inch ones would be 235/45/18 and those are at 793 rpm (continental conti sport contact 2). The difference is about 3 percent which means if you were doing 103 with the18 inch rims in reality it would be 100mph if you still had a 17 inch rim setting set on the car which is really too little bit of a difference. To answer your question, no, ford does not have a different tunes for the 2 of them. They only adjust that one tire setting just like you would on an SCT calibrator.
P.S. going by the overall diameter is inaccurate when it gets to things like reading the vehicle's speed, that's why the set with revolutions per mile instead. If you need rpm specs on your tires just message me and I'll get them for you. Oh by the way. As your tires wear it affects rpm and also the overall diameter so just from that you'd get a or so percent difference on the speedometer reading on new tires vs the old ones.

 

Do the math with the tire calculator.
The 16" stocker rims/tires are the
same diameter as the 17" OEMs
with Perillis and the 18" stockers
are also almost the same diameter.
Its somewhere around 720 Revs Per Mile
for the OEM speedo patio set-up.
Now aftermarket rims/tires are a whole
new deal. But all the tires/rims options
OEM are all about the same as to
the Revs Per Mile or diameter.
Just the rim gets bigger and the sidewall
gets smaller.

 

+1 and +2 also
Heck, +3

 

You are completely mixing this up...RPM = REVS PER MILE in this case not revs per minute and is what setting you play with in the tuners generally, therefore diameter is VERY accurate when you are trying to fix your speedo. if you keep your diameter around 27 inches then there is no need to change the setting, you speedo is correct.

 

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You are completely mixing this up...RPM = REVS PER MILE in this case not revs per minute and is what setting you play with in the tuners generally, therefore diameter is VERY accurate when you are trying to fix your speedo. if you keep your diameter around 27 inches then there is no need to change the setting, you speedo is correct.
[/quote]
yea, revolutions per mile is what i meant, because obviously revolutions per minute would depend on what speed you're going at. sorry.