Hey everyone, I am currently running 35x12.50R20 pro comp extreme all terrains on my truck. The tire size is currrently programmed to 2356 in my edge, does this sound right??? I'm trying to make sure my speedo is caliberated right. If my dash speedo says i'm going 85, my edge will say 82 or 83 (usually 3 off) BUT, my garmin gps will say 80 or 81 usually? Is the gps right? Or do I have it programmed wrong at 2356? Help please, thanks guys.
I heard the dash speedo will always read a lil high but i'm not sure.

 

The dash speedo IS going to read higher than your Edge OR the GPS. Your goal is to get the Edge and the GPS to agree. If you do, your dash odometer will be correct and your dash speedo will be reading about 2-3 mph faster than you are actually traveling - call it speed trap insurance.

So, it seems your Edge is reading 2 mph HIGHER than the GPS? I'd trust the GPS here and, I KNOW you do not have 2356 set in for Tire Size (TS) - that's a "placeholder value".

Try a value of 2709mm. This should be your TS in millimeters allowing for about a 3% "squish" due to the weight of the vehicle on the tires. And please READ this sticky CAREFULLY: https://www.f150online.com/forums/ch...ions-menu.html It tells you how to use the Custom Options Menu. (Make sure you actually PROGRAM your PCM - I doubt you're doing that.)

- Jack

 

Thank you, Jack. It's kinda confusing sometimes because when i set it up back in March when I got my lift, I went to custom options-tire size and I think I remember it showing 35x12.50 and i selected it. And tonight when i went into it, I saw the 2356. But, I will enter the 2709 and let you know what happens. Once again, thank you for your help.

 

After reprogramming the tire size for 2709 I took it for a 6mile trip thru town and on the interstate. My edge and gps matched perfectly. The dash speedo read just slightly higher than both. Thanks again, Jack!!

 

Sounds like you got it "nailed". Good on you!

- Jack