I have the latest superchip flashpaq for my 2014 rubicon. When I checked the tire size, it had 30.1, however, I have the stock 255/75/17 which are 32.1. When I changed it to 32.0 the speedometer is now of by 4 mph. If I have 32's then what value do I need to set?

 

The tire size you enter should reflect the actual measured tire after mounted under the JK and inflated to the psi of choice. Use a tape measure. You will see that the tire measures less mounted under your JK then it would sitting next to it. Its that simple.

 

I have "35's" on my rig, but the speedo didn't read correct until I set it to 34's.

 

you'll have to play with it a little and check the speedo against a gps. My 35's measure 34 mounted and loaded on the Jeep, but I had to set the super chips to 33 to get it to match the gps speed.

 

Measure from the ground to the center of the hub and multiply by 2 to get your actual wheel height for the computer. Measuring from the ground to the top of the tire will be too much.

 

I didnt think of that. You are wise and I learned something.

 

Is it necessary to buy a tuner to correct for tire size changes. Or is there a easier way. I have a stick 2010

 

Yes, you need a tuner.

Thanks, measuring the tire helped.

 

Something has to be done for the computer to know what the tire size is. Buy a programmer, buy a tuner, or pay the dealership. Most people say the dealership can only calibrate for stock tire sizes, (though one person recently indicated that his dealer programmed for 35's), so maybe that's worth a shot if you want to pay them instead of having a unit with a lot of extra features that you can use any time you want to).

 

My dealer tried to get the speedo right but could not he could only get within 4 mph. Not until I bought a superchips flashcal could I get right on. And do it like it was said above, to the middle of tire multiple by 2. It works perfect now.

My question is, Superchips wants me to upgrade for $179 to the flashpac by down loading it. Is it worth it? What exactly do you get that is useful?