Tire Size
 

Should the tire size be set at actual size according to the chart or allow for a "squish" factor. I currently have the stock 255/70/17 tires inflated to 37#.
I have the tuner set with a 3% squish factor that I have read about in some threads on FTE. Was wanting to make sure the setting is correct to get accurate benefit from the tunes. Thanks.

Mine is set with "squish". You DO need to include this correction if you want the speed and odometer readings to be correct, and, it will have a small effect on your shift points which can effect the benefits of your tunes. I've subtracted about 3% from my tire's "unloaded" circumference and find that to be about the right amount. My tires are 275/65R18s and they are inflated to 40 PSI.

Whatever value you try, it's a "starting point". The way I first calibrated mine was on a trip to California on the interstate. Over a distance of 100 miles (using highway markers - which are quite accurate) I found I had less than 0.1 miles error on the odometer. Later, using a hiking GPS with WAAS, I found the Gryphon's and GPS' speed matched (while the dashboard speedo read 2MPH faster - it always will read fast).

My guess is, you MAY have to increase your "squish" factor more for the tires and pressure you use. Let's say you tried the "distance" test like I did and found your odometer read 101 miles after 100 actual miles. That would be a 1% error, so, you could subtract an additional 1% from your tire's circumference.

Hope this makes at least a little bit of sense!

- Jack

So you're saying that the squish factor isn't really related to the amount of road kill you encounter while driving .......yuk yuk yuk ! :hehe:

That COULD be more of a "bump" factor! :cheesy smile:

- Jack

Well....I don't know about this technolgy stuff...I am suppose to have my new programmer delivered on Monday, but now I am getting a little scared about installing the dadgum thing....all these postings about trouble with starting...camshaft settings ...running too lean on canned tunes with CAI (my customs most likely are gonna take another 2-3 months), battery needing a external charge if the thing stays plugged in....tire size....tire pressure (don't know, the darn things are filled with nitrogen is all I know) ...squishin $hit.....tweekin this.....torquein that!.....geez.....hell I have to type all this stuff with two fingers as it is !.....only mechanics I do is hand me a BFH and stand back, anymore! Looks like ole Bill may just get a call before I start connecting anything....I havn't talk to anyone on the phone at PHP as of yet.....reminds me of when I was just teenager.....DAZED and Confused ....oh well! Story of my life I guess

If you need to chat, let me know when it would be a good time to call! We're here for ya! :grouphugg:

Thanks Corey...I have been putting off calling until I really get my programmer due to some info I needed to get to Bill so he can do my customs (ASAP!!!:cheesy smile:)....I am really not as overwhelmed as I seem....:lookaround1:....I did have my truck into the dealer after I first got it (4000 miles) over what they told me was a plug and coil pack problem from the factory ....they fixed it (after a couple of trips to the dealership...(22000 miles ago now)....I am pretty sure they reflashed it then ...and I am not sure after all the *****in I did that they didn't bump up the tune on it to compensate (runs pretty damn good, I was worried about the programmer maybe messin that up).....anyway...like I said ...I'll call sometime after I get the thing on Monday....wifey and I are headed to see her family down in San Antonio this weekend ....I was hopin for an early delivery to go play in the sand in Port A.....awwww well....next trip for sure ( I get down there often)...yesssss!

:censored1:oooooops sorry about the slip of language.......my wife (who is a high school teacher) gets on me all the time....but it's hard for us ole dawgs....

got a quick question when bill does the custom tunes, does it come already program it for the gear ratio and size of tires we state on the order form

We normally set up the tire size and gear ratio as part of the custom tuning.