BlueJeans161

So we have all read 200 threads about resetting tire size when you install a lift/level and bigger wheels and tires. I have a new twist on the old story...

I have a 2014 F150 SuperCrew with a level and 315/70/17 Cooper STT tires. Love the look, but the tires are getting close to the end of their life. I have found myself pulling a trailer a little more often and am thinking for the longevity of my tranny (and in the interest of saving a cool 1200 dollars), I'm going to go back to my factory wheel/tire package.

When I put the bigger wheels and tires on, I had my local Ford dealer plug into the computer and change the factory tire size in an effort to correct the speedometer/odometer. He charged me 40 bucks. It was two minutes worth of work, but better than the 125 other dealers wanted.

Fast forward 3 years, I have moved, and I cant get a dealer to touch it for under 100 bucks (which is highway robbery). I did however, have one dealer offer that even though the tire size is changed, the way Ford calculates speed with revolutions/min, that really doesn't do anything. He told me to throw my factory wheels and tires back on, and if the speedometer was right, then the odometer was right, and I shouldn't lose sleep over it. Unfortunately, that's not how my brain works.

Is there any way you all know to reset tire size BACK to the factory setting? Will unplugging the battery and resetting the PCM achieve this? Can I do this with Forscan?

Thanks in advance.

TJPlatinumEB

Ha that Ford guy is absolutely wrong. The speedometer and odometer work "together" so to speak. If one is wrong, they are both wrong. Going from 31.9" tires and then up to 35's then back to 31.9 will be a huge difference in speedo/odometer. It needs to be changed and your brain works better than his

Unplugging the battery doesn't do anything unfortunately. It is programmed into the PCM so it doesn't change that. However, there is a spot in Forscan to do it. I have mine changed with a tuner, but haven't looked to see what Forscan says in there. I've read that some people aren't able to get it to work via Forscan and some do. Worth a shot at the very least. Cost you all of $30 for the module to run Forscan and you can have it for the future for any other issues or changes you want to make.

BlueJeans161

Thanks TJ. I guess I should have been a bit more clear: my speedometer is off right now. GPS says I'm going 77-79 when I'm at 70 on cruise. I made the tech show me the setting and my actual tire size in the computer when they did it...so its changed, but my speedometer never has been accurate.

Its not just the speedometer that concerns me though. I don't want to be running up more miles on my truck than I actually am because I put smaller wheels/tires on. I know speedo and odometer are supposed to be linked, and maybe I'm just being OCD, but I'd like to have it 100% right.

bgrd351

Honestly, and Im sure a bunch will chime in the same, just buy a tuner. You can get more power, etc etc and set your truck to whatever size you want via the revs per mile of your actual tires.

It wont be much more than what dealer is charging for just changing the speedo to a factory setting that is closest to your size. Dealers cant set to off size thus why your speedo is off.

There are several tuner venders including one on her at a sponsor that sells unlocked tuners for a big discount.

Spiky

I think you read that wrong, TJ.

But, BlueJeans, since your speedometer has been wrong all this time, that means your setting was never actually changed. Changing it back with forscan is the best for "your brain", I'd say. It's quite simple, that item is set up in forscan as a menu instead of needing you to change hex.

TJPlatinumEB

Whoops yeah I read that completely wrong. My fault. Wrong time of year for me!

llangarica

If you have a Forscan setup currently, you can get your 'As-Built" data for your truck for free from ford. Compare the data with the As-Built data sheet to what forscan says and adjust accordingly. There's tons of good info on the sticky at the top of this sub forum. buut as TJPlatinumEB said, I have also read about people changing tire size with forscan not working for them. Your absolute best bet would be to get a tuner. You adjust tire size plus you would get a bit more power as well. WIN WIN!

BlueJeans161

Thanks guys. I think I'm gonna give forscan a shot before I look at a tuner. My dad runs a used car dealership and he told me he has the OBD2 bluetooth scanner, so I'm only out 5 bucks for the app if it doesnt work.

RLXXI

The app can only read/erase codes and watch streaming data, to make changes you have to use the Windows version and I strongly suggest you not use Bluetooth when programming, too much risk of data corruption, this is the usb cable I use. .

Spiky