Changing tire size

[Slopjock78]

Ok, so I've got a fairly simple question, and I probably could have found the answer if I would have looked a little harder.....

anyhow, I just sent in my Gryphon yesterday to be reprogrammed from a 5.4L gas to a 6.4L diesel. My question is this: i have put on bigger sized tires then stock, can I personally change the tire size once I get the unit back? i was always under the impression that i could, but wanted to make sure.

thanks for the help
slopjock78

[Longshot270]

Yep, no problemo.

If you have a GPS you can also get the tire size perfect with a simple formula.
Truck odometer divided by GPS odometer and that multiplied by the current tire size entered in the programmer. The answer is what you enter into the gryphon.


If you have pegasus there is a nifty little tool called "Gear ratio calculator". Just put in the current tire size (ex 255/70-17) and eastimated tire squish and you can get really close to the actual tire size.

[Slopjock78]

Perfect!! thanks a ton longshot, that is exactly what I was looking for.

So I should be getting my S&B CAI today, and hopefully my newly programmed gryphon sometime next week.... Then i'll be getting close to having this 6.4 running the way it should be

thanks again

[Slopjock78]

so I finally got my gryphon back last night, and so far couldnt be happier with it!!!! definitely worth the small waiting.

so i went to change the tire size, and a notice came up that changing the tire size would not affect my speedometer. which, i'm assuming, means that my odometer is still off as well. I'm a little more worried about that cause i would like an accurate reading on my mileage.

is there anyway to change the odometer and speedometer that are actually on my truck, not on the gryphon??

thanks for the help
slopjock78

[Longshot270]

If the gryphon can't change that then the only option is you might have to have the dealership reflash it. If you look around you might be able to find a OBDII tool to recalibrate for bigger tires. I think I remember seeing something that can change that but I dont know what it will do with the tune. You can use the MPH parameter on the screen for your MPH reading but I'm not sure about the odometer.

[jasfaa]

Dealer cannot fix major tire changes as they only have a few choices to make electronically. I asked and they tried. I am still off by 10 mph at 60. I wish it were as simple as the old days. Just changing the gear on the end of the speedo cable.