Thread: Gryphon won't correct tire size
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Old Sat, January 30th, 2010, 11:33 AM
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Originally Posted by btownford View Post
I had custom tunes by PHP, but my computer was reflashed 2° new motor being installed. I have an 05 F-150 with a 06 motor. I updated my gryphon to the canned tunes offered through Pegasus. I install in truck and every is a go except for the tire correction. I have 285/70/17 and inputed 2610 and hit enter. i check back before programming and it saved my tire input mm. When i go to program my speedometer is 7mph fast according to GPS. When I go back to reprogram truck I load previous settings and everything loads except for the tire size and it reverts back to 2356mm or whatever. I tried it atleast 4 times without success. I updated to the newest firmware and calibrations prior to tuning everything.

Anybody have a clue why its not doing my tire size correctly?
It MAY be because you are "checking" the Tire Size (TS) BEFORE loading the tune, or, you may be looking at the TS BEFORE you "Load Previous Settings". but first, the TS value you are entering is too large, which is what is making your speedo read so fast. (If it were actually programming in the 2356 figure, your speedo would read SLOWER than you were actually doing). The 2610 figure is correct for an unloaded tire - no "squish". You have to reduce that value to account for the "flattening" of the tire on the pavement which reduces its effective radius. I've found a 3% reduction works well, which in your case would be a value of 2532mm. However, if your speedo is 7 mph fast at highway speeds, you probably need to reduce that value even more, maybe to about 2453mm (which is a 6% squish).

Now, to get the Gryphon to "show" you that the TS is correct: As soon as you OPEN the Custom Options Menu - scroll to and select "Load Previous Settings" and hit <Enter>. THEN, scroll to TS and hit <Enter> to see the value, then hit <Enter> again to accept it. (Don't push the <Menu> key in any of this and DO NOT go to the TS entry before you "Load Previous Settings"!

Don't be surprised if the TS is just a bit different after reloading the previous settings. If you had entered 2532, I predict you will see 2534 after reloading it due to rounding errors (it's not a big deal).

Let us know how this works out for you, OK?

- Jack
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