I have a 2011 Wrangle 6 speed. I got me a procal and set my tire size as required and my speedo is still off. When I put my 33's, I was 2 mph slow. I set the tire size to the measurements and it 2 mph faster. I dropped the tire size 1/4" and it's still the same. Does anyone kknow at what point do you measure from end to end?

 

Measure from the bottom of the tire to the top as the Jeep sits on the ground to get the most accurate measurement. It'll be less than 33".

 

I did it that way....it was 32.75". Stuck that in and I was faster then my GPS.

 

^ i have 33's too and I have not used my procal yet. but it shows in the AEV book to measure your front wheel mounted height, not the spare. it should be about 32"

I am not sure I was going to use the procal, with my 33's my speedometer is dead on.