That would be a good question for Rock Krawler.
On mine, the stock rear springs each have the same part number, indicating no compensation for the gas tank.
Also, my JK weighs the same left and right with half a tank of gas, further indicating no need to compensate.
The front springs are not exactly the same, the right one being one digit higher in the last part number position. (Maybe to compensate for the high torque of the 3.8!)
Each front wheel is supporting the same weight there, too.
Last edited by ronjenx; 12-23-2011 at 06:04 PM.