Not sure whats going on but got new tires which are different size then the stockers.
Edge and Speedo read the same.
Passed one of those digital speed signs that tell you how fast you are going. Read the same as the edge and the speedo.

Techincally it should be off.
Went to a couple of tire sites to calculate the diff in speed. One tells me I should be going faster, the other tells me I should be going slower.

So Im at a loss.....Thought maybe I would update the edge for the correct tire size but im not sure what to do or to leave it alone.

 

You can probably leave it alone, but:

The Edge has "programmed" your PCM already to think you have a certain gear ratio and tire size. Have you confirmed your gear ratio is right? Maybe, this is just a "two wrongs make a right" situation.

If the Edge has loaded an incorrect gear ratio - I'd correct it, and then set the tire size (accounting for "squish"). Edge's default gear ratios don't seem to be what you got with your truck from the factory.

- Jack

 

Crap cant find my book, where do I go in the edge to check the gear ratio?

Truck is running 3.73

 

OK, if you know your truck has 3.73 gears, that's probably what the Edge is using for defaults too.

Go into the menu, then select a "custom" option and scroll into the gear ratio and tire size options and set them. (Maybe, the Edge default settings match your tires and gear rato)!

You can get an Edge manual here: http://www.edgeproducts.com/installa...structions.php if you can't find yours. It says it's the installation instructions, but it's really the operators manual.

The manual has tire circumferences for "standard tires". Reduce these by 3-5% to account for "squish". Do a road test, and if it's right - go with it.

- Jack

 

Alright found the book and had some time to go thru the motions.
Heres what I found.

For both Lvl 1 and Lvl2 I got the following.
Gear ratio is set at 3.73
Tire size says 2356

Book says for 275/65/18 tires - 2559
If you take 3 or 5% away, assuming I did this correctly then I should have 2483 or 2432

Ive never messed with the custom settings, so either edge is set this way for performance issues or something got screwed up somewhere/sometime.

On another note I checked a couple Online tire calculators out for the new tires, and I get a number of 2650. However if you look in the book for a 33inch tire it says 2632

So wheres this leave me, other than confussed ???

 

I would use a gps to confirm your speedo error (or not). If you don't have one maybe borrow one from a friend. Once you know if your tire setup is correct or not in the edge you can do the math to correct it.

 

Screwdude, I also have 275/65R18 tires with a 3.73 axle. I've been using 2481 for a tire circumference and it seems to be "very" accurate. The factory speedo is 2mph fast at 75 but the Gryphon/Edge is correct and the odometer seems correct. I've checed mine with those radar signs, my handheld GPS and the old-fashoned way of dividing distance by time. All three methods agree. My tire pressure is 40psi.

As I recall, before I got my custom Gryphon tune, the default tire size it wanted to put into the PCM was 2356 also. Maybe this is a "stock" tire on some f150 models.

I'd go with the "calculated" 3% value as a start. Check the speed and adjust from there.

- Jack

 

Cant really see why they would put a smaller tire on these trucks but guess its a possibility.
I guess im questioning if they used that tire size due to the nature of the Tune. To get the extra performance out of the truck?

Concerning your second paragraph. Not sure which way you are thinking by your response, but
For the 33's
2649 x .03 = 79.47
2649 - 79 = 2570

 

I think you may have misread my reply. I have 275/65R18 tires. The edge manual says the unloaded circumference is 2559. I found, through testing, that a circumference of 2481 gives me correct speedo and odometer readings. This corresponds to about 3% reduction from the "unloaded" circumference.

I can't comment on your remark about 33s, since I don't look at the tire size that way. I simply use the metric sizing. I recommend you do it this way too.

- Jack

 

Hey another question, when adjusting tire size (or any custom options) does it have to be done when first setting the tune, (ignition on,off,on), or can I do it after the tune has already been set and running.

 

Any change has to go thru the on, off, on process. That step is necessary for reprogramming. There is an option to chose in the custom settings that saves all the settings, so that you do not have to go thru resetting every item, just the one you want to change.

 

Ok so I assume that the adjustment that I did (tire size), while the truck was running didnt do anything. Even though it asked me to set a custom file?

 

Actually, I do not know, but it would scare me to try it. What if you did it going down the road, when would the computer make the change? I think there is a reason you have to turn the key off then back on.

 

It would scare me too - for two reasons.
If you "Load Previous Settings" as the first step in creating your "Custom Tune", you'll be able to see what tire size (and gear ratio) has been saved and plugged into the PCM. Of course, you'll also see any other changes you made. If you don't "Load Previous Settings", the Edge is going to start you with its defaults, not what you've set before.

- Jack

 

Wasnt changing the setting while driving, just parked in the driveway. Guess what I meant was I already had it programed for Lvl 1 so I just went and changed the tire size. Without doing the on/off/on thing.

1. Not understanding your "Load Previous Settings" comment. I dont find this option.

2. I started from scratch. Reset back to stock. Turned truck back on let it run. Then went to level 1 programing said yes to custom file. Set the tire size to 2570. pressed "done" and waited, turn on, then started truck when it was ready.

3. Did the same for level 2

4. Went back into custom options for level 1 and the tire size says 2356
5. did the same for level 2 and the tire size says 2356

So is something still not right or is it just reseting to 2356 because im going back into the custom options?

Is there a way to check the tire size setting after it is set without having to go into the custom options?