On motorhomes, there are Five types of tag axles. I have the fixed type that dumps (actually reduces the bag pressure) to reduce the load for turning or backing up to reduce scuffing. A second fixed type will actually lift the tag tires off of the ground to eliminate scuffing. A third type has "Passive Steering". The tag tires will steer only because they are being forced in the opposite direction that the MH is turning. The fourth type is "Active Steering". This one is connected with the drivers steering wheel. If you turn the steering wheel to the right, the tag wheels will turn to the left helping to swing the rear of the coach. The fifth type used on Gas motorhomes. Its suspension can be a rubber spring that just carries weight and does lift or steer.
All five types will carry more load and add to the stability of the MH in adverse wind conditions. They also help smooth out the ride.
2013 43 QGP Allegro Bus
CJ7 Rock Crawler