Changing tire size on my tuner

[smokinsrt]

I purchased an Edge Evolution a couple years back and I was never able to get my tire size to save on it. I switched to the Gryphon and put on my order form what tire size I was running it came back with the proper size on it. I bought some new rims and tires for the winter and they are smaller once again I go in to make my change and when I get back into it it hasn't saved. Whats the deal? Anybody ever had this problem am i not doing something right, a certain step to save the change or what?

[shotgun]

You can't view your tire size or gear ratio, you can only change it in Custom Options.

Jack has created an excellent sticky explaining the Custom Options menu. It's imperative you follow the instructions to the letter.

http://forum.gopowerhungry.com/faqs-...ions-menu.html

[smokinsrt]

Thanks for the quick reply and the link but that still does not help me. When I go in and make my change then go to done and it loads when I go back in it still shows the old size has it changed and just not showing it or what?

[shotgun]

Originally Posted by smokinsrt

Thanks for the quick reply and the link but that still does not help me. When I go in and make my change then go to done and it loads when I go back in it still shows the old size has it changed and just not showing it or what?

As I said above, you cannot use Custom Options to display the values. They will always revert to the canned or stock valves.

Q: I switch programs from stock to an advanced level tune and when I go to check my Tire Size (TS) and Gear Ratio (GR) in the Custom Options menu, I find one or both of them is always wrong! Why?

A: The Custom Options menu was not written as a tool to "check" any value. It was written so that you could make changes to some of the parameters used in your tune. Since the Custom Options menu was designed for you to change things, it loads simple "placeholder" values into the tune for TS and GR and it is probable that one or both of these is incorrect. You will need to replace these placeholder values with correct values if you find that they are wrong. These placeholder values are entered for TS and GR right away, just as soon as you OPEN the Custom Options menu.


Q: But why can't the Custom Options menu load my correct values for TS and GR instead of the incorrect placeholder values?

A: It will, if you immediately scroll to "Load Previous Settings" and press [Enter] as soon as you open the Custom Options menu. This will recover and reuse all the option settings you used in your last tune. It is a quick way to get back to where you were before. From this point, you can make further changes, which are saved in a revised "previous settings" file. Please note that if this is the FIRST time you've opened the Custom Options menu, there are NO "previous settings" to reload.


Q: OK, I tried reloading my "previous settings" but now it says my TS is 2484 mm. I KNOW I entered 2481 the last time! Why is the TS different?

A: This is because the value needed by the PCM is not really Tire Circumference, but Tire Revolutions per Mile. The programmer converts your TS to Revs per Mile but discards any fractional result. So, even though 2481 is actually about 648.667 Revs per Mile, it stores the value 648 in the previous settings file, and plugs 648 into the PCM. When you "Reload Previous Settings", the programmer converts 648 back to Tire Circumference in millimeters which is about 2483.556. This is rounded to 2484 in the display. While these rounding errors are not really significant (about 0.1%), you can easily correct them if they bother you.


Q: What if I just skip the Custom Options menu when I load my advanced tune. Will my TS and GR be correct then?

A: Yes, if you haven't installed different sized tires or changed your gears from the OEM sizes. Bypassing the Custom Options menu causes the tune to load TS and GR values that are stored in the VID section of the PCM.


Q: I read somewhere that we should bypass the Custom Options menu the first time we load an advanced level tune. Is this correct?

A: Yes. The first time you do "Power Programming", it is best to skip Custom Options entirely. This allows the programmer to read the original calibration from the PCM and allows it to build all files it will need in the future.