After searching awhile through the forums I could not find but a few mentions of 235/80/R17's which seem to be the stock size for my truck, that's what's on it and thats what the door says should be on it.
What I've been looking for is the height the tire should be. Mine are measuring at 29-7/8" (Ameritrac), but there is a heavy nose gooseneck hooked up to it and I've been meaning to check the tire pressure on them. The problem is I they should be bigger than my dad's 235/80/R16's but his back tires measure 30 -1/2" (Hankook) while his front tires (Yoko's) that say the same size finish at the same as mine do.
What got me started at looking the tire sizes is I have an Excel spreadsheet that I have been making that will tell the speeds and rpms of certain transmissions and height of tires as well as we have been thinking that my dad's truck is the one that is off on it speed and mine was right.
So...does anyone know their actual tire height?

 

Look for info on the tire manufacturer's websites.

 

different brands can vary in size and tread depth

 

What I am looking for is the actual height of the tire in inches and I can't find that on any of the websites.
What are some of the bigger tires the duallys are going to that do not require spacers?

 

www.tirerack.com might give u the sizes

find a tire on the site then

look under specs http://www.tirerack.com/tires/Spec.j...m%3D38R7AMTRAC

 

Already been there and haven't seen that. I found one that calculates and gives everything in cm, but that is why I am asking for what other people have for measurements, I want to compare what people actually have vs. what it should be.
http://www.kouki.co.uk/utilities/vis...ize-calculator

 

Different tire manufacturers have different sized tires.

Saying 235/80 is vague, as tire sizes may actually measure 239/76, or 231/83. They just don't get that precise or people would freak out trying to figure out which tires they need.

That said, speedometers aren't that accurate either. If it's within a few percent you're doing good.

So you need to ask the manufacturer what the revolutions per mile are for their tire. Bigger tires spin less, smaller tires more.

For your excel sheet, just use a calculator and input the revs per mile and you'll figure the correct speed for any tire made.

 

Well finally got the trailer off so I rotated and aired up my tires, the left outside dual was down to 12psi so that would explain the 29.8 inches I was seeing, now their up to 30.9 inches, still not exactly where they should be but much better.
That 12psi tire left an imprint on the inside dual, might also explain why the inside tire was so hard to break loose.