Here are a few calculators that may be useful in deciding tire size, gear ratios, and other stuff.

http://www.4lo.com/4LoCalc.htm

ENjoy

Cool thanks Russ ...wow my new BFG 285/70/R17 are 32.70866141732284 inches. guess they must call these 33's.

Hey Stan, I think you and I have the same tires now. I got the 06 aluminum rims and tires from a guy, used, for 400 bucks total.

Damm Russs what did you do beat the guy up thats a friggin sweet deal one of those rims would be 400 greenbacks or 377 Can bucks lol ...yup we have the same tires and rims now ...didnt have to beat that old guy up to be like your bigger brother moose from Canuckville

LOL.. Nah, I know I got a great deal, they had abou 4/32 of the thread worn off of them when I bought them used. But the rims are bad ass! I will be having my bro powder coat them in black this winter.

They guy actually had them for sale for 450 and took 400. He has an 07 and likes the hummer rims, so he was looking to unload them quickly.

Our trucks should have came at with 258 the 265's look tiny on such a big truck. I love the look of 285 not sure if i have the tire size set right on my superchips though, what is your set to Russ ??

Drive train ?
yeah, I did for 38 years. Now, I'm retired.

I set it to 33 inches.. I believe before it was like 31.75 or 32.

Cool thanks Russ im going to check it today

Good stuff! Apparently when my speedo says 60, i'm actually doing 70.. Time to reset the superchips!

Tire height has been discussed a lot. The way it should be done is actually measure the height of the tire on the truck. I have the factory 275/60 20's. I used the tire size calculator figure of 33" when I first used my Flashpaq and my speedo read too high. I should have left it at the factory default of 31.75". When I set it back to 31.75" the speedo was ok again. Ron at Superchips verified this info over on the Flashpaq forum.

quote:

Tire height would need to be physically meassured from the ground to the top of the tire within 1/4" with a measuring tape.
Ron

http://www.flashpaq.com/forum/viewtopic.php?t=1577

Here is the actual formula to get the exact height of your tire:

Yep. Problem is the height returned from the formula doesn't take into account the amount the tire is squashed down from the weight of the truck. I've thought about that aspect of the issue for a long time. Using the squashed-down measured height really doesn't make much sense to me because the rolling distance for one revolution is the same whether the tire is on the truck or off the truck. The circumference of the tire seems to be the important number to me. That will be the same regardless of air pressure or even if you take the tread off the tire and flatten it like a tank tread.

true Hemibyrd, but once moving, do the tires balloon out and return to their original size? I know when the funny cars get up to speed the ballooning effect of the tires changes their gearing (granted they are moving at 300 MPH, but there still may be some degree of change in our trucks at say 60 MPH) Just stuff I think about during the day.. haha