post your true tire diameters
03-13-2014 | 04:34 PM
#23
JK Freak
Joined: Jul 2012
Posts: 548
Likes: 0
From: United States
I have 255 Rubicon BFG MT. I measure the rolling circumference and divided by PI. This gave me the diameter of 30.75. I programmed my Procal with that number, and the speedometer is right on the money. I checked it with 2 different GPS's.
03-13-2014 | 05:18 PM
#25
JK Enthusiast
Joined: May 2013
Posts: 100
Likes: 0
From: Seattle
Measuring to the bottom while parked may be different when park than when in motion though correct? Wouldn't centrifugal force cause the center of the tire to expand thus creating a different radius/diameter? May be thinking of this wrong and or maybe change is so minor that it doesn't matter
03-13-2014 | 05:21 PM
#26
JK Enthusiast
Joined: May 2013
Posts: 100
Likes: 0
From: Seattle
This would likely be the most accurate way to calibrate a speedometer but ... for the reasons mentioned by Planman, not an accurate way to measure resting tire height.
