Ford IDS - Can the dealer change factory tire size?

[Fordiesel69]

So there is no confusion, im not asking about aftermarket tires and rims where you need to do a customer tune for sizes that were never listed for the vehicle.

But lets say you have a ford that has factory steel rims with LT245/70/R17, and you end up buying nice alloy rims on CL with new tires and they are factory 265/70/R17, that is enough to mess with the transmission shift points, in addition to the speedo being off. Because the trucks shipped with many sizes those two being on the list, is this possible?

Dealers tell me not. But I have seen screens online with IDS where there is the ability to select tire sizes. Which is it?

 

[BISCUT]

Not positive but I believe ForSCAN can do just that.

 

[FordBroncoVWJeta]

I was playing with Forscan on a new to me 2019 Ford Interceptor Sedan. There was options to change tire sizes, but only for a few select tire sizes. The Taurus came with 245/55R18, there was options for sizes such as 235/55R18 and 245/45R20. It seemed limited to tire sizes that would come on other trim levels.

There also was options to change the tires MM and other specs. You might have to download it and play with it as it seems to be vehicle specific what options you can change.

 

[dumkid]

If you move up in tire size without changing anything else, the transmission will generally shift at the same rpm or slightly higher rpm, but at higher road speed. Most transmissions learn your driving habits and adjust where the shift points are accordingly. I bet the different tire sizes in forscan affect the speedometer/odometer reading though

 

[bdcardinal]

Not any more. EPA regulations related to emissions. I believe if it was a factory option size for that vehicle that year they still might be able to.

 

[Dave9]

That's only a 3.6% difference. I wouldn't give it another thought, though if you want the speedo more accurate than that, yes a dealer or Forscan can potentially change it to the largest value wheel/tire size offered for that vehicle and potentially get that 3.6% down lower if not exactly right.

These nice new rims, they have an appropriate offset, hub opening diameter and stud spacing?

im not asking about aftermarket tires and rims where you need to do a customer tune for sizes that were never listed for the vehicle.

Then what are you asking, if it can run the same size that Ford put on as an option? Of course it can. If you want the correct values to reprogram the speedo, I'd ask in the approprite Ford-specific (truck?) forum. Someone may have the spreadsheets for your m/y to use with Forscan.

 

[Fordiesel69]

That's only a 3.6% difference. I wouldn't give it another thought, though if you want the speedo more accurate than that, yes a dealer or Forscan can potentially change it to the largest value wheel/tire size offered for that vehicle and potentially get that 3.6% down lower if not exactly right.

These nice new rims, they have an appropriate offset, hub opening diameter and stud spacing?



Then what are you asking, if it can run the same size that Ford put on as an option? Of course it can. If you want the correct values to reprogram the speedo, I'd ask in the approprite Ford-specific (truck?) forum. Someone may have the spreadsheets for your m/y to use with Forscan.

Then why am I asking..........Im taking my steel rims with not so good LT245/70/R17 for a set of very nice aluminum rims P265/70/R17 and the speedo would be off.

I already know / knew if you go and buy some big sand dunes / mudder tires the dealer cannot do anything for you.

 

[MNgopher]

The other thing to watch out for in your proposed change is going from an LT tire (Load Range E in that size) to a P Series tire. The load rating on the P-series is lower and has to be further derated. Depending on the configuration of your truck, you may actually need the load range E tires to maintain the rated capacity. Those tires typically came on payload packaged trucks.

 

[Hall]

Not positive but I believe ForSCAN can do just that.

There also was options to change the tires MM and other specs. You might have to download it and play with it as it seems to be vehicle specific what options you can change.

I remember seeing menus related to tire sizes and allowances for tweaking. Can't remember if there was a "manual" option that let you plug in details that weren't pre-populated though.

That's only a 3.6% difference. I wouldn't give it another thought

I agree. At 60 mph, the speedo would be off by 2 mph.

 

[meep]

I am pretty sure forscan allows some tire size changing. Especially if that size is available that year, I’m pretty sure it can. I’d want to plug it in and verify if it’s important to you.

I don’t know if the f150 would be super sensitive to that tire change. I did this to a Jeep grand Cherokee (WK) and the transmission could hardly ever find lockup and fussed between 4th and 5th gear - it was bad. But the f150 grabs TC lockup in 3rd in my 2018 and I suspect would not complain as much.

 

[cb_13]

Not after 15 on F150s. I’d say the capability to do so on Superduty probably disappeared around the same time. I was told it was epa related. Before that IDS gave the option to choose between factory sizes. Going back even farther it gave the option to input rotations per mile for an almost endless amount of size options.

Forscan has circumference adjustment for many Fords. It seems to work a little differently for every model though so I’d do some vehicle specific research on that one.