Can someone explain how to do this? I want to use program 2 and change the tire size to 35" but when I look at the custom program it has all the parameters set to 0 so my question is: If I change the tire size without changing the other settings will it use the level 2 settings and use the new tire size to make the speedo correct or do I have to change all those settings? If so, what are those other settings suppose to be set to?

Also, the smallest tire size it will allow is 1750 mm which doesnt make sense because my 35" tire is equal to 889 mm. What am I not understanding about their conversion of inches to mm? Did a google search and found that it wants the circumference which is 2791 mm so I'll fix that in the morning.

 

You can just set the tire circumference, save and exit (with the menu key). No other tuning values will be changed. Once done if you use another custom level you will have to change the circumference value with that tune also (I think). I have the Gryphon unit, If I change to different levels I have a selection to load previous values, this may re-load the tire size you have entered. If I am not correct with this, someone will correct me. Go Here and enter size: http://www.rimsntires.com/rt_specs.jsp

 

the manual has the value there that you should use for 35s, but they don't allow for squish. I would use 2792 less 3%, or 2708. You don't have to change anything but the tires and make sure it defaults to your correct gears. If it does't, change the gears, too. You must have those two things correct for the programs to function correctly.

 

yep, it did use the 3.73 gear ratio and I set the tire size to 2707 so I'll drive it tomorrow with my phone gps app and see how close it is. If it doesnt seem right I'll get my wife to drive next to me.

Thanks for the help guys. Just didnt want to mess up the programming before asking.

 

Just a note, the speedometer on the truck is always 2 to 3 mph fast. There is no need for her to drive beside you. Set Edge/Gryphon to display the digital speedometer and adjust it until it agrees with the GPS. The thruck speedometer will probably read about 3 mph gaster at 65 to 70. I never look at the truck speedometer. I use the display entirely.

 

The only problem with that, admittedly it might be minimal, but your mileage is calculated off the speedo, not the handheld/phone GPS. Wouldnt it be prudent to have the speedo set as accurately as possible?

I went through this hassle when I first got the Edge, and it seems that my truck as developed a memory because I havent touched the tire size in ages and anytime I check the truck is bang on accurate as the GPS. Any thoughts?

 

To amplify on what Bluejay said, when the dash speedo reads 2-3 mph fast, the odometer seems to be dead on. The odometer is digital, while the dash speedo is electromechanical and has errors caused by that process.

Bluejay's TS is the value I'd start with. You may have to make further adjustments. A low profile tire has less "squish" than a high profile one. And, tire pressure and vehicle weight have an effect too.

- Jack