Got my Gryphon, Got Cpl Q's

[tg150]

Hello all..

I appologize for never mentioning the size of my previous 18" wheels and tires vs my 20" wheels..

the 18's were P275/65/R18
the 20"s are P275/55/R20

After i installed the Gryphon on level 2 i took my truck for a drive like Jack suggested "Before" going into my "Custom Options" and changing the TS and GR, which turned out to be a great idea. My trucks speedo was approx 1-2 miles faster than the gryphon so i figured i must have been right on from what i read. But i wanted more proof so i went home and got my Garmin gps and sure enough the MPH on the gps and the gryphon matched exactly. So come to find out there really is no difference between the oem 18" wheels and oem 20" wheels.

Overall i love my gryphon..i did notice and improvment in perfomance, quicker shifting and responce.. I cant wait to get my 87 performance tune.

I'd like to thank everyone that replied and helped me figure this out and hope this post helps others that might be wondering the same thing. TY..

Jack.. a special thank you to you for accepting my PM's and walking me through it step by step all day long. Your a great guy and i really appreciate it. TY..

Corey.. Ty for being so polite when i called and answering all my emails quickly.. I enjoyed all the goodies that came along with my Gryphon and it sure made my day

Thank you everyone..
-Tony

[Jackpine]

Thank you Tony, you're quite welcome, and, thanks for posting your tire sizes, so I could find out something for sure (not that I doubted you Lars)!

Here's what I get for the two tires using Bill's super easy calculator in Pegasus:

No Squish - Stock: 2559mm, 20's: 2545mm (a 14mm difference - about 0.55 inches, just as Lars said)!

5% Squish - Stock: 2503mm, 20's: 2498mm (a 5mm difference - only 0.02 inches)

7% Squish - Stock: 2480mm, 20's: 2479mm (only 1mm difference - virtually identical - only 0.004 inches for those of us who are metrically challenged)!

As I've said in other posts, the 7% rubber squish seems right for me with my 275/65R18's inflated to the recommended 40 psi. That's why I recommend it as a starting point.

Tony did not set his tire size when he loaded his tune - he bypassed the Custom Options!, so, the tire size was a "stock value" taken from the PCM's VID area. Clearly, Ford allows for "squish" too. And, interestingly, when squish is factored in, the two very different tires cover virtually the same distance in each revolution!

Again, thanks Tony, for confirming your tire sizes so I could explain what happened (to myself at least). This is a pretty neat bit of data to add to the database!

- Jack

[88Racing]

Thanks Jack for posting the info.
The aftenoon break was to short for me to put my pencil to the numbers and post them.
Someday I will get a laptop with an air card to do better posts instead of the blackberry.

Lars