air fluctuation Normal

2005 Columbia single axle, I have recently started running the truck with a air ride trailer for the first time, trailer is building pressure normal, now it reaches 125psi air dryer purches normal, now my question is which I had not noticed before once traveling on a interstate is it normal to loose 5-10 psi in air fluctuation on the air gauge with the bouncing around on the road? mine does but it builds right back up. it does it empty or loaded.

 

I have left the air system built full pressure after releasing the valves and I don't loose pressure at all, so to understand the whole time going down the road not touching the brakes, I should always see 120-125psi on the gauge? as the air ride is leveling out as you travel down the road doesn't this cause the pressure to drop thru the release valve on the trailer?