[Jackpine]

They have such faith in me, don't they, tg150? :o Hope it's not misplaced.

Yes, I would go ahead and enter whatever program you decide on and bypass the "Custom Options" choice at first. Why? To be honest, I really don't know. But, it seems to be the way to go.

When you do this, your factory gear ratio AND factory tires will be loaded into the appropriate areas of the PCM.

As I understand your post, the factory gears are 3.73, so, you can leave them alone. The tires, though may need to be changed, but, Lars could be correct - the net effect may be a wash.

I'd do it anyway.

So, once you've programmed your PCM, you can start all over again. Go ahead and select the SAME tune Level, but this time say "Yes" to "Custom Options". When you get that menu open, scroll down till you find "Load Previous Settings". Hit <Enter> there to make that happen. Now, scroll to the "Gear" setting, hit <Enter> to open it. It should be 3.73 - if so, hit <Enter> to confirm it. (If not of course, change it to 3.73 and hit <Enter>).

Now scroll to the "Tire Size" and hit <Enter>. You should be seeing the "factory tire size" if I understand the way this works now. I'd be interested to know what you see at this point, so please make a note of it and let us know.

I've looked at Bill's calculator and I come up with a value of 2479 mm for your new tires with a 7% rubber "squish" (the "flattening" of the tire that reduces the effective radius when there's weight on it). Your number, 2546, was absolutely correct by the way! But that's the distance your tire rolls in one revolution when it is not "flattened". This "squish" correction is just a guess though, and it's what worked for me. Anyway, I'd try 2479 at first. Confirm somehow, with a GPS or radar sign if the Gryphon speedo is correct. If it is, your dash speedo will be 1-2mph faster, but your odometer will be correct.

If your speed on the Gryphon is slower than you are really going, you need to increase the circumference value that you enter next time. If it is faster, reduce the circumference value still more. You can do this by trial and error, or, if you can determine the percentage speed error, simply change the tire circumference by that percentage.

Remember to "Load Previous Settings" as the first step from now on in the Custom Options menu, so that you reload any other changes you made.

Make sure also, that you hit <Enter> at each setting you reset or accept to same them, and then, scroll to the "Done" selection and hit <Enter> there to start the actual programming process.

Sorry, I know all this sounds a bit complicated, but I can do it in my sleep now. I't really not that bad once you get the hang of it.

Have fun!

- Jack