I searched the forum and couldnt find anything about this, just how to calculate tire size. I got my Hypertech yesterday and am planning on installing it today, my question is what should i do about the tire size. The book says it goes in .25" incriments and the tire size calculator I used that I beleive steve linked to in another post says my tires are 32.83", so.. should I program the computer for 32.75" or round up and program for 33"????????

thanks
JIM

 

id say 32.75 cuz its closest to it

 

If you do 32.75 your speedo will read a little bit slower than you are going. Likewise, if you program 33 your speedo will read a little faster. It shouldn't matter a whole lot either way unless you often push the envelope in terms of the tolerances of the cops in your area. Where I live, if you get a ticket and a calibration shows your speedo to be off by the amount you were speeding, they will knock it down to faulty equipment (a non-moving violation). I have a Superchips programer. I hope I never get another ticket, but if I do I plan to use the tire size feature to weasel out of it.

 

lol....

that tire size calc is based off a fully inlfated tire or a tire thats off the rim...

if you read through the hypertech book..it stats make a small mark on your tire with chalk and a corolating mark on the ground to math that mark..now drive forward untill that mark you made on the tire hits the ground again after 1 tire revolution.. mark the ground again...take a measureing tape and measure the distance between the two marks in inches..and divide that by pie.. 3.14 to find the TRUE diameter of the tire... and match that to what the computer says your tires are in inches... the measurement you get with the method i just mentiond will be more exact to what your truck actualy sits at as well as your actually tire diameter...

this will change with different tire pressures and tread wear....although tread wear won t be a significat factor unless somehow you turned superswapers into drag slicks... lol

 

or you can go here http://www.differentials.com/calc.html
and punch in the size...

 

Yeah, I went to that link you posted steve, and it gave me 32.83". Maybe Ill do that whole chalk thing like the book says, just a PITA though.

 

i'd do the 32.75... better to have your speedo read on the high side... (speaking from a guy who has not 1 but 2 tix in the last 6 months in the ram... and 0 tix in a pretty fast (for a 6 cyl anyway) M3).

 

So, I reprogrammed my truck tonight after work. I went with 32.75" for the tire size, and Ive only got one thing to say.. HOLY $#!T, Ive got a HUGE NOTICEABLE difference! And Im just running the 87 Octane program.. I LOVE IT!

 

Good deal. You probably had what I like to call the "bean counter flash". When I first re-progged w/ my Superchips, I had the same feeling.My truck came stock w/ the flash and the difference was night aND DAY. You have to try the higher octane program. Some say the difference is neglible, but I tried it and stuck with it. I have gone back and forth with the two programs, always w/ high octane fuel on both, and have noticed a big difference @3000rpm +. Just make sure that, after you fill up w/ high test, you run about 20 mi. or so before you reprogram for the higher octane.