STANMAN

Is it easy? There are like zero instructions that came with mine, and I don't want to screw up the tune, as that's obviously much more important, lol!!!

Hufenstang

i have been trying to figure this out also stan, i just got new tires and my gauge is off now. i will let you know if i find out any info on it.

STANMAN

There's lots of good info on these boards, someone who knows will chime in for both of us!!

undefeated

I don't remember seeing the option, but if it's the same as when I had to change the gear ratio in the tuner, it goes like this....
When you go into "Custom tune", it'll eventually ask you if you want to "change parameters", or something on that line after you select the tune you want.. Then, you push select for"yes"and you page down till you see the tire size option, "Gear ratio" in my case. Once you go in there, you modify it. After you modify the parameters, then you push Cancel to get out of it and it'll ask you if you want to "Save entries". After selecting yes(select). You should be asked to begin the tune loading.

GT4HUTCH

Bruh, if i am not mistaken the way to change the tire size is to enter your new tire's revolutions per mile. You can either get this number from the tire manufacturer or do the math yourself. Custom Tune, select,change perameters, revs per mile.+/- Hope this helps youout.

HUTCH

Scotty07

Hutch has it. You can rev's per mile. You can find rev's per mile on the tire manufacturers site (well, most of them anyway) or through places like Tire Rack on the tire's spec page.

The rev's per mile changes are done in incriments of 5, which is close enough! Example, mine are 769 and I chose 770

I also had to change gear ratio on mine since I went with 3.73's. Comparing with GPS mine is now within .5 MPH @ 60 MPH.

Hufenstang

i tried to change my parameters today, but it never gave me the option when loading my tune. Is it possible that when i got a custom dyno tune at the shop that he locked this feature?? im not sure what to do =\

Scotty07

Sounds like you may be locked out.