Brady_bot

Anything you'd recommend to get the speedometer closer? Had my gps on today and at 65 mph on the gps speedometer read 80-85. Gears are correct, I don't see where I'd enter tire size in mm as my edge just has me enter it as 35/12.5/20. Anyone have any ideas? A few mph off is no big deal, however 20 mph is.

08silverbullet

You can use 87 as long as you don't advance your timing

RajunKajun59

Actually it makes perfect sense. While you may not be changing the tires circumference squish changes the rolling circumference. For instance if you measure the radius of an unloaded tire you get its actual circumference, but when loaded measure the radius to the ground and it will be shorter, therefore reducing the rolling diameter and rolling circumference. Hope the explanation makes sense, if not I can try my hand at a picture.

Brady_bot

Last night I changed my measurement to 33.6" instead of 35", accounting for 4% squish.. We'll see if it makes a difference at all. Really hoping it does.
Edit:It's still way off. Just changed it to 33.2 or 2651 mm. Don't think it'll make a difference though.

F150_Life

My Edge asked my for my tire size in mm.. is there a way to put it in as 35x12.5x18?

Brady_bot

Mine had 5 options, I could do it like 35/12.5/20 or 315/70/17 or by mm. There was a few other options as well.

Brady_bot

I realized my speedometer wasn't really off to begin with before the programmer and having 35's. So I set the tires back to "stock" even though they're 35's. Bingo. Speedometer is dead on now. Little confused but oh well, guess that did it.

F150_Life

Dang, mine only gives me the option to do mm : / unless i'm missing something?? I know I read on this thread something about how to calculate your tire size in mm... but it didn't make much sense. Can someone explain that to me?

Brady_bot

I believe you do your tire size in inches (35) times pi (3.14). Multiply this number by .97 for the "squish" factor, then multiply that by 25.4 to convert to mm. So it'll be (35x3.14)= 109.9, (109.9x .97)= 106.6 , (106.6 x 25.4)= 2707 mm. So you should enter 2707 mm for 35x12.5x18 I believe, someone please correct me if I'm wrong. I saw this in an earlier post while looking for myself.

stmar

I am having a similar issue, not as drastic but speedo and tripo are showing faster/farther than true. I have changed tire size as you did and still cannot get it to calibrate. Setting it to stock is a few hundred mm less than actual but may try that and see if it works for me. Have any other EVO users had a similar experience??