Do all coaches with tag axles have a option to lift the tag ? If not, how would you know? If you are viewing coaches online. I would figure that if I was seeing a coach in person I would be able...
My vintage Prevost has just regural pressure regulator (common in shops for adjusting air pressure going to tools). I never played with it, but that sounds like what you are talking about Dennis. On the other hand, when I drove main axle into the ditch and tag got overloaded, I start hearing over-pressure valve popping, so there is a limit how much you can play with it.