You have to go with your running diameter, NOT the tire diameter. Measure from the center of the wheel to the ground. Double the number (radius).
That is the actual rolling diameter.

 

For the purpose of setting your tire size in the Flashpaq or Cortex, this is how to calculate the value you will input into the programmer.


A. Measuring my tire in order to adjust the “Tire Size” setting.

Solution: Measure your “Tire Size” vertically, and place a ruler or a flat, level item on the top of your tire in order to measure accurately. Measure your vehicle’s Tire in inches and round up to the nearest quarter of an inch.

Note: “Tire Size” includes tire and rim. Please ensure tire is inflated to manufacturer recommended pressure.




Hope this helps.


Sil

 

Not that it would matter much, but lasstss's comment is more accurate than the method of measuring to the top of the tire. In figuring out the circumference of the circle the truck is 'rolling' on you need a circle with a radius that is the distance from the center point to the ground. To get diameter, if that's what the programmer needs, you double that radius value. Measuring to the top of the tire gets a number that is a little too big because the top of the tire isn't squished like the bottom is.

Rob

 

I wish I could play with the TM settings.......

I have yet to have the ability to download the upgrade. My update software has a blank screen still under "vehicle 1". The coupon has come and gone, 2 tickets to tech support, and numerous emails... Still no upgrade for me.....

Anyone else in this situation??

 

That's what I love about forums, you get to hear everyones opinion...when I say everyones I mean peeps who know nothing and peeps who do. When a man tries to share his knowledge like Sils is which by the way is the correct way to calculate your gear ratio people should listen. Instead they try to explain how he is wrong and they are right. I've argued this same poo poo over a year ago when some of you guys had claimed it was the tire size and some even went as far to claim that it was the rim size....it's tire height! Now it's expanded and deflated tire size huh...BS, the weight on the bottom of the tire forces the tire at the top to expand so either way Sils is the more accurate, lol! If you want to get real technical, the tire height increases dramatically at high speeds causing even more tire height. Look at dragsters coming off the line...you will see the slicks go from say 30" high to 33 plus in a matter of seconds. The tire narrows in width and increases in height which changes the gear ratio using slicks giving you a top end edge. In other words if you can't brake the slicks loose and they hook up (no spin), the faster you go down the quarter...the more the tire expands in height giving you more top end changing your gear ratio. None of you knew this back when I brought it up a year ago, now everyones knows, lol! If I were SilsHemi, I wouldn't waist my breath trying to help you guys who say other wise. I don't mean to be a horses **** but gees, give the guy some credit here. He's gone out of his way trying to help all of you with the tuner...least you could do is show some respect and listen to him. One minute your pleading for his help and the next you rain on it...gees!

 

yea, that's what I was thinkin, thanks !

 

After playing with the truck for a couple of days, I have to say that I'm very, very, very impressed with the Superchips. With the suggested advanced options running, the truck is a totally different beast. WOT is so much different that it's almost scary.

While horsing around with WOT is fun, I've got to hand it to them for the every day drive-ability of the truck. The changes in shifting while just cruising make the truck glide through acceleration like a luxury sedan. Stock settings have the shifts way too hard, but the Superchips changes make it seem smooth as butter. Another thing that I love is that MDS is finally off on the truck. While I'd use it for long trips, tooling around town it seems more of a headache than providing any assistance. Seemed like every time it was on and I needed to give it a little gas just to make it up the next small it, the truck sounded like it was struggling to make it up. MDS is dead, long live MDS!

While I enjoy a lot of the small mods I've done to the truck, I'd have to say the Superchips is probably the most bang for the buck so far. I love what it's done and I'm already dreading putting the Stock tune in before I have to take it to the dealer next time.

Oh, and thanks for the help with the tire size. I guess my math skillz just aren't what they use to be.

 

Since you don't have a great grasp of geometry let me try to clarify things for you. A tire on a wheel travels a fixed distance for each revolution of the wheel. If the tire were 100% solid and didn't sag at the bottom where the weight of the truck pushes against the ground it would travel the circumference of the outside of the tire based on the overall diameter. Since it does sag, the actual circumference is based on the diameter of an imaginary circle centered at your hub and that has a diameter 2x the radius from the hub center to the ground, taking into account the tire sag. What the top of the tire does matters not one damn bit in the measurement of circumference.

If you want to fuss about me offering my opinion on this that's fine. That's what the Internet is all about. If you want to contradict me super. Everyone can have their opinion. I'm likely not going to convince you and I really don't have to. As long as physics is what it is and geometry follows the basic rules it has always followed then there is only one correct answer. You choose which one. Also, Sils seems to have offered tons of great info here and is a super resource. I don't disagree at all. And his suggestion for tire height measurement is the simple and easy one for folks who want something simple. It works and it is really close. It just happens to not be 100% accurate but that really doesn't matter a lot. I just described the more accurate method in case anyone cared.

By the way, peeps are the spongy marshmallow things we get at Easter. I love Peeps!

Rob

 

Other than that weird 5500rpm shift, this truck is pulling harder than it's ever done before. Also got to really test out the new TM setting today and love it. All I got to say is when it downshifts hang on!

 

War Horse, glad you got it going, I know exactly what you mean about removing it , I hate taking it out, the shifts suck with out it, are you running the 91/93/87 tune?