I just got the edge tuner and need to change my tire size on it, their 305/50/20 nitto terra grapplers, what size would i change that to on the tuner.
thanks guys

 

I used this conversion site, http://www.miata.net/garage/tirecalcold.html and took the mm size*.03 and then subtracted my answer.

Ex, my tires and edge setup

285/70/17=2610mm

2610*.03=78.3

2610-78.3=2531.7

2531.7 is pretty close, I fine tuned with my GPS and settled on 2532. The mechanical speedo will always be 2mph faster than the edge digital readout no matter what you do.

 

Ftruck05's method is exactly mine too. I subtracted 3% for "squish" from the unloaded (round) circumfirence and then adjusted a little bit from there. My final setting is still just about 3% less than the conversion site's value.

You MAY have to subtract more than 3% or less. It all depends on the construction of your tires and their inflation pressure. But, 3% is a good starting place.

- Jack

 

does 2477.7 sound right, i dont know if i did it right for a 305/50/20

 

pretty close, I might say 2475.

 

thanks for the input guys,

 

every time I input my correct tire size (2559mm)........when I go back in to make other changes and I check the tire size again, it for some reason has changed to 2563mm-wtf???

 

mine does the same thing every time i input 2475 and save it i go back to look and its back at 2335 again.. ????

 

I programmed in one size smaller and this time when I go back in and check.....tadaa....my correct size is in there! I out smarted a computer.
It seems to automatically change to the next closest size up or it defaults to the closest available size programmed into it for some reason. Now that's just plain stupid!

 

Yes, it will always revert to what is in the program. That is the default setting. You have to first tell it to restore your settings if you don't want it to go back to all defaults.