WWII HiStOrIaN

So I have new 32's on my truck that I just upgraded to from the stock size on the stock 17" rims. Do I need to put the new tire size in my edge to correct the spedo or is it fine? I have heard mixed reviews.

Mod (Ret.)

Depends on how much off the speedometer is, and if that's a concern to you. There are freebie sites you can access (tire store web sites) that allow you to enter the stock size tire/rim, and then the new size tire and rim, and it will tell you the difference in the speedometer at 65 MPH. My guess is that yours is going to be off by about 2 miles per hour at 65 MPH reading of the speedometer.

But since you have a tuner already and will adjust for this, why would this even be an issue? If you did not have a tuner, then I'd understand not wanting to spend 300 plus dollars just to correct a speedometer issue.

dhonnoll

Do the math, it is always percentage based. If you have 10% taller tires, you roll 10% further for every revolution so with the speedometer at 55mph you are driving 50mph IF your tires are 10% taller. if your speedo is at 60mpg you are traveling at 66mph in that instance. Find out how much further you are driving per revolution in percentage and it is easier to calculate at any speed. Or you could spend 1hr labor and have the stealership calibrate it. I miss the way the old 92-96 could be calibrated at home. But I don't think I am going to get taller tires though.

WWII HiStOrIaN

Well the only reason I ask is because as of right now I don't have the truck tuned to any of the power levels. I have in the past and intend to again but I don't want it like that full-time. I didn't know if there was any way I could set the new tire size without tuning the truck to a power level. I know it seems dumb but sometimes my truck is for work not play lol.

Mod (Ret.)

You should not need to install a "tune" in the truck to change certain parameters, such as a speedometer adjustment. Many tuners allow you to make adjustments to the speedometer (based on larger tires), and do so with a completely different menu in the tuner. My cheap Superchips tuner allowed for this.

What brand tuner do you have? See if it appears when you connect it to the OBD II port of the truck; there may be a menu that shows up on its screen that allows you to to adjust for larger tires (and other possible adjustments), and would not require that a tune be installed to do this; would be two separate functions of the tuner.

Darkstarskater8

I recently got an edge (Gryphon) and had them fix the wheel size for speedometer in my custom tunes. I have been 5 off over 50 mph for the past 4 years and the faster you go the more its off.
I believe you just reload the tune but click yes create a custom tune and enter the size in mm's.

HOW TO CALCULATE:
[(width X ratio X 0.02) + (rim X 25.4)] X 3.1416 X 0.97 =
tire circumference IN MILLIMETERS