My guess is they should lift to equal heights off the ground. That being said, I am not sure if there are two airbags, air shocks, or whatever, that control the push-down force on the tag axles. I know years ago I relaxed the push-down force to lighten up the weight on the steering axle on our RV. So... if the air pressure works to push down on the tag axle, then what mechanism lifts and holds up the tag axle when it's supposed to be in the lifted position, such as, when backing up or driving slowly forward or when the tag axle lift switch is activated?