Well, just installed 35's, pics here https://www.f150online.com/forums/wh...19028-35s.html

Problem is when I went to change tire size with the Gryphon and got a message about not supported yet need update or call support... something like that. So I downloaded the update utility Pegasus, and while it seems it installed ok, when I try to open it only displays the splashscreen that says initializing, the screen disappears, and no software LOL.

any help will be appreciated. was going to call PHP but see they are on vacation. Not a big deal as I compared to GPS and am reading 3mph slow, but would like to correct and use tuner to full extent.

If it matters, I did buy this used from a forum member who said he bought this year, and have been using a tune with no issues at this point

 

This sounds a bit like it could be a firmware problem in the Gryphon. But to correct it, you need to have a working version of Pegasus.

Completely uninstall Pegasus and, with whatever registry cleaners you have try to get rid of all traces of it. Also, make sure all the directories used by Pegasus are gone.

Download a new installation file from PHP. Also download and READ the installation directions! Try to install it and run it without connecting your Gryphon. Then, IF if runs, click on [Update]->[Pegasus Update Manager] to download and install the latest revisions to Pegasus (there will be some). Finally, with Pegasus running, plug your Gryphon (at Level 0) into the PC and attempt to update it's firmware and calibrations with [Updates]->[Gryphon Update Manager].

If you're still having problems, you need to bring this up on the PHP forum.

- Jack

 

Thanks Jack. I had already tried to reinstall the software, but your post made me realized could affect the registry, so I did a "restore" to a point before the install, re-installed and all is good!

Updated Pegasus, then when check for updates of Gryphon, it said was up to date. But I decided to reload anyway and after that was able to do the custom load to adjust for tire size.

HOWEVER, I never did figure out but for trial and error what number to input for tire size. I had to input in mm, and when I converted inches to mm, it was around 889 if I recall correctly, and the Gryphon only went as low as about 1700 mm..... Anyway, through trial and error I set at 2600mm and it is now dead on.

So I hate to ask, because I feel stupid LOL, but how was I supposed to compute?

 

Glad you got it figured out, Bob. I keep forgetting about "system restore", probably because I don't use it too much. There DO seem to be hiccups in installing Pegasus, and I can't figure out what they are (I keep trying though).

As far as your tire size, there are several ways to figure this. First, if the tire sizing is metric, there is a tool in Pegasus called the "Gear Ratio Calculator". If you enter your tire size like this: "275/65-18" (my tires), and change the "squish" (flattening effect due to vehicle weight of the rubber) to 7%, you'll come out with a value for circumference in millimeters that is very close.

If your tires are "inch" sized (and I see they are, following the "picture" link), multiply 35 x pi x 25.4 x 0.97 = 2709mm. Here, I'm reducing the unloaded circumference by only 3%, because I'm accounting for the fact that the rims don't "squish" like the rubber does. You calculated the diameter in mm correctly, but you needed the circumference.

Now, your tires have fairly "tall sidewalls", so I actually expect the squish effect to be more than the 3% (0.97) value I gave here. But, I doubt it's quite as much as the 2600mm figure you came up with. If you get the TS right, the dashboard speedo will almost always read about 2mph faster than actual speed, but the odometer and the Gryphon speed will be right). I'd actually suspect a value of 2650mm might be more accurate.

However, whatever works, works!

A final way to calculate TS is to use an online reference like Tirerack.com where they give the "revs per mile" figure. This is the page for your tires: http://www.tirerack.com/tires/tires....omCompare1=yes Click on the "specs" tab.

The Revs per Mile number, 597, includes "expected" squish. So, 5280 x 12/597 gives the number of inches (106.131) traveled per revolution and that can be converted to mm. I get 2696mm this way, so that's still pretty close to the 2700 figure.

Hope all this makes sense!

- Jack

 

Thanks so much Jack.

Hmm, circumference.... never made the connection Mr. Obvious LOL. Makes total sense now that you have spelled it out, and I am sure with more research I could have found this info already posted here somewhere... so really do appreciate your effort.

I probably will adjust up to 2650 or 2700, i was just trying to find a balance that wouldn't rack up mileage faster than true and I do like the speedo reading a couple MPH than actual to give me some "speeding cushion"