Wyocountrykid

Hey guys I'm posting this topic as a last resort. Hopeing to find a clear answer from someone. After researching all around the internet and on every f150 forum I could find. And talking to multiple dealers and well established truck modification shops around the area I've not been able to get a clear answer on how to fix for tire size. But I have learned a lot.
I have a 2011. It came with 30 inch tires. The tires I put on the truck are 295/70/18 (34.26 inches). As the speedometer and the MPG and the truck miles all correlate to the tire size, all these are thrown off by my aftermarket tires. Now I understand its "showing" Im putting on less miles than I actually am. That my MPG is better than what its showing. That my speedometer is off. And I know how to calculate the true numbers. I can live with all that. Thats not a big deal to me.
Now what I was trying to fix was truck performance. Which is where my real question lies. Can I fix truck performance and how? Mainly meaning can I fix how my transmission shifts and overall truck performance by a Dealer reflash of some sort.
Here is what I've done and what I have learned. And PLEASE correct me if Im wrong as Im looking for answers.
The speed sensor on the F150 is in the transmission. All the calculations related to this are derived from here.
Fords new transmission is "self learning" meaning over the time you drive the truck and how you drive it the truck adapts to you.
Fords computer reads the VIN to know which ratio and tires the truck has and how to perform via the VIN number.
Fords IDS only lets you change things in the parameters of Ford factory options. So knowing this I went to a local dealership and asked them what they could do for me. Their answer "well we can see how close we can get it" not very assuring so I didn't go through with it at the time. After more research and somewhere on the internet a savvy F150 owner suggested most aftermarket tires people run are 35's, the Raptor is in IDS, flash it to raptor 35's. I thought I had found my answer. My tires are as mentioned earlier 34.26, raptors are 315/70/17 (34.36). I went back to the local dealership asked if they could flash it to raptor size, it is in fact a stock size and very close to what Im running. Problem solved?
Now after $93 bucks and a dealer Flash nothing has changed. All my readings are the same MPH MPG ODO. The only thing that seemed slightly different was the shifting for the first day, but it was ever so slight almost imaginative. I drove for a week to see if maybe after some time my transmission would "learn" the new tire size and maybe feel better. It feels the same.
Now Im searching for answers. I intend to take my truck back to the dealer. Im hoping that somewhere maybe someone as came across something that worked or has a better understanding. Something that improves trucks performance with the added perks of correcting tire size readings. Im wondering now if the reflash even works since the truck reads off the VIN? Or if the dealership can change something else to correct for this. Ive talked to several dealers about maybe "lying" to the truck about which gear ratio and tires size it has in it to correct for my tire size. They told me it cant be done because it reads off the VIN.
The LAST option will be a aftermarket tuner. And thats when I reach the lowest low, when nothing else works. So low that I gotta reach up to touch the bottom . haha! It is a new challenge... and I LOVE a good challenge!
So what can a dealer do for me? Seems like my options are trickling down to; 1) its as good as its going to get from dealership help, 2) aftermarket tuner.
But anywho guys sorry for the novel and any help, input or advise is appreciated. Maybe this can help others guys in the same boat and give us all a better understanding. Thanks

Fatmattyd

Unless I'm reading this wrong, it sounds like a gearing change.

By changing the tire size (circumference), you've effectively lowered the final drive ratio.
Without actually calculating the real numbers, it's like having gone from a 3.55 rear end to a 3.31, or something like that. I'm not sure on the raptors, but don't they run 4.11 gears?
Seems like everything would come back in line (gauges, driving experience, etc) with the appropriate gearing change.

I'm not sure if there's a software fix for any of this... maybe with a tuner? Others with more experience can chime in. If you want to change the performance back, however, I think you'll need to look into changing the ring and pinions (both front and rear if its a 4x4). I'm surprised no one mentioned this previously (dealers or truck shop)... makes me think I missed something in your post.

Good luck,
-Matt

Wyocountrykid

Thank you Matt for the response. I have looked into new gears for the truck when I was putting the tires on it. I was looking at 4.10's. I ultimately decided against it because it is around a $1200 dollar modification. Also there was a very interesting post on gears and the new transmission on this website https://www.f150forum.com/f70/2011-5...3-73-a-117187/
My calculations and yours are very close. My truck has 3.55 and with 34.2's it comes out to equivalent of having 3.20 gears with 30 inch tires. Or factory 3.30 geared truck. From the mentioned post above I decided that the modification wasn't worth the money to me. I was hoping to find a software fix that cost less and was a easier fix.

msgtord

What is your reference as to the accuracy of the speedometer?

And how far off is it now after the flash.

techrep

iTrader: (1)

Damn...just buy an EDGE and be done with it. You can input your exeact tire size and a whole lot more.

150driver

Unless the IDS options have changed for 2010 and up, there should be an option to go in and change the total circumference of the tires and wheels. That is what I did and a good friend of mine who also works here at the Ford dealership with me, but were also driving older trucks. (Mine is a 2000, his is an 02')

Smoke Eater

That's what I am wondering as well.

To the OP how did you measure the distance driven, only use the ODO or did you use a GPS as a second means to accurately measure how far you drove as well as the MPH.

Because if you are only using what your truck instruments are showing you then yes of course they will be showing the same.

You have to remember, adding any sort of lift, changing rims and tires will most likely affect the results of your MPG.

You seem like a pretty smart dude so hope you get it figured out soon enough, and let us know what works for you.

Lama

I just did the same deal on my 2011 5.0 / 3.73 truck.

Had stock 245/75-17 tires, "Off Road" package.

Went to 295/70-18 Trail Grapplers

Speedo was severely off, shift points were strange, MPG calculator was weird.

Took it to dealer. They charged $99.00 to reflash my speedo.

Sure enough, they fixed it, as the speedo is within 3mph beteween 60 - 80mph, the shift points now feel normal, and the MPG indicator seems more accurate.

Thus I do believe there is a way to run large tires on the IDS system, contrary to other posts that say you can only select a tire size that is within your vehicles VIN number range as a "stock size" tire.

Or.......the technician at my dealership altered my final drive ratio setting in the IDS, and that is how they obtained the speedo recalibration.

I looked at my paperwork, all it says is "recalibrated speedometer", thus I don't know for sure.

Smoke Eater

https://www.f150forum.com/f38/real-f.../?ref=esp-link

Take a look in this thread, lots of good info from just a few weeks ago I believe.

AC Man

Is there any way a local garage would have the ability to reflash for my larger tire, or would only a Ford dealer be able to do this?