x2 I asked AEV this very question, whether to measure center cap down and multiply by 2, they said ground to top of tire. That is what I did and it is spot on with my GPS.

 

With or without the wight of the jeep on the tire? Those numbers will typically very an inch or more... depending on the air pressure being used.

 

Inflate the tires the way you will run them.
Follow the steps in post #10.
Nothing else will matter.

 

The chalk line will work too. That also factors in true roll radius. It is Quicker and easier to factor in center to floor x2. I know aev says the over all height of the tire but that is not accurate for the overall height due to compression on the tire. Hence, the center to floor is slightly shorter than the center to top. I did check with GPS. 3 different units actually. The center to floor x2 worked spot on. Doing the aev recommendation is off.

 

I found that with my manual trans, that the DRLs come on with it in gear and clutch out. When I come to a long stop with the trans out of gear and clutch released, a minute or so later, the lights go off until the cycle is repeated from stop light to stop light. So with an Auto that most people always leave in D, they would stay on until parked.

 

With the weight on the tires at the psi you will normally run (for my 2012 that is 37 psi).

 

Wow, 37 psi? I run 25 psi on the street on my 35s. Big tires are made for 10,000lb trucks, not 4,000lb Jeeps. I set my TPMS to compensate. I actually set it at 10psi as I could never tell if my 33s on my old TJ was low until below 10. That, and I can air down for the trails to 15 in the dry, 10 for the snow and not trigger the system.

 

This is why some guys can't figure out why their 35" tires are 33" mounted and loaded Use manufacture specs and it's like a free lift kit

Regardless of size, a tire's handling and durability is directly tied to using the appropriate inflation pressure for the vehicle. With a variety of wheel and tire choices for new vehicles, it's essential to rely on the vehicle manufacturer to specify the appropriate inflation pressure for the tires. Using the vehicle's weight capacity for each axle and other considerations, the manufacturer can best calculate the psi needed to ensure the tire handles and performs well.

All too often, many drivers and mechanics assume the maximum tire pressure listed on the tire's sidewall is what is recommended for proper inflation. However, that number represents the maximum pressure that's safely allowed, but is likely higher than what is recommended by the vehicle manufacturer.