Front Drives Off The Ground?

I have seen this twice now, both times at truck stops.

Typical 53 foot combo rigs, no heavy haul or extra sets of axles, and axle 2 drives (front) aren't touching the ground. The latest one I witnessed must have been nearly 2 inches off the pavement , on level ground. It was VERY obvious, yet no one seemed to notice, or alert the driver, or frankly seem concerned.

I'd like to know what causes this in case it ever happens to me. Am I missing something simple?

Thanks for any insight.

I haven't seen this on a tractor, but I guess it's an automatic lift axle similar to what I have on my flatbeds. The axle automatically lowers when needed to carry the weight. Under a light load the axle lifts to save wear and tear and fuel.

Max weight in the nose of the trailer, 5th-wheel set to the rear of the tractor frame (unnecessarily) and all the air released from the drives suspension. Low air pressure in the drive tires could also contribute to this.

Can't think of anything else that could cause this in a well maintained truck. Once the truck is started and air pressure returned to the bags it will level out.

A rookie tendency I've observed is to run with the 5th-wheel locked in the last set of holes furthest from the cab. This makes for a lighter weight on the steer axle. Balance as close to 12k as possible when fully loaded requiring the 5th-wheel set closer to the cab.

I misread this...the front Drive set tires are raised or the steer tires. If it's the drives, definitely a lift axle in the raised position.

Thx guys...yea g-town, the front drives. Thanks for the explanation. I knew there had to be one!