i think you're talking to a wall - that's come up and been explained quite a bit but nobody ever seems to remember. the H3 doesn't have a portable programmer to recalibrate it, so you need to have the PCM reflashed. the H2 can be reprogrammed with a few different handhelds. i don't even try to explain it any more . . . . . .[X(]

 

So, are you saying the gas mileage gets worse (with bigger tires) only because you are driving faster than you think?

 

the computer thinks your mileage is getting worse than it actually is. the added weight and power needed to get bigger tires moving may negatively impact your mileage some, but not as much as your computer thinks. when the odo says you've gone a mile, you've actually gone farther than that, and are going faster than the speedo reflects, so it can't keep up. i changed the tire size in the bus computer when i went to 37's and compared it to my GPS, i'm only off by about 2 mph when on the freeway. mileage dropped from ~10.7 to 10.2 mpg after programming. the pcmforless pcm upgrade for the H3 can be set to account for the correct tire size, and there are multiple programmers for the GM 6.0 liter that work for the H2.

 

Very nice choice. I have the same tires and lift on my 2006 for over a year now and I love them.

 

Geeze!!! It's such a simple concept I can't understand why some want to complicate it. A larger tire has a GREATER circumfrence than a smaller tire. Thus if you were to rolleach tire One revolution the larger tire would roll further than the small one. The same thing happens on your H3 when you change tires. Your speedo is calibrated for the tires it came with from the factory. When you install larger / smaller tires without recalibrating the speedo it throws off the odometer and you will NOT get an accurate mileage reading ever again unless you use your GPS. I don't want to hear about "My mileage went to hell" after a tire swap when it hasn't changed at all. There are plenty of shops all over that calibrate speedos. Your local State Police may be able to give you info on who does it because they occasionally have to point folks to the shop to avoid another ticket.

"That's all I have to say 'bout that" [sm=rant.gif]

 

i had a friend drive beside me so i could see hor far off i was. when my speedo said 50 i was doing 55..

 

Yep!! 10% faster then what you see and 10 % less on the odometer. I had Toyo MT 33's last year and the difference was only 2% but now 10% with 35's

[hr]

H3 2006 LUX, ARB Locker, Full skid plates, Toyo MT's 35's, Rock sliders, T-Max winch, PIAA lights

 

This might sound stupid but a smaller circumference gives you faster acceleration right?

 

How is the wear with the toyo mts i am between them and goodyear duratracs

 

Yes... smaller tires can boost acceleration.

I used to have a TrailBlazer SS... the one with a LS2 Corvette-derived V-8... came with 20-inch wheels... a popular mod for TBSS drag racers was to switch the 20s for lower profile 18s to get better launch and acceleration on the lower end.