Dump valve question

Lift axle only make sense if you have long deadhead legs or toll considerations. On a big spread tandem a dump valve on both axles might be your best option. You’ll still need to be able to dump both sometimes for unloading heavy pieces or unhooking and that would let you choose which axle to dump when dumping one.

 

Use rear axle dump, ft. axle lift

 

Ideally, you should be able to dump either axle at will. Sometimes you'll want use the front. Sometimes you may use the rear. However, if I had to pick just one it would be the rear axle.

 

The company I drove for had their trailer setup that way. It was kinda a PITA when you were at a dock and wanted to have the air out anyway. The airbags would deflate and the trailer shift forward from the change in the suspension. you would end up 1-1/2' away from the dock when the are was finally out. Then you wanted to release the brakes and back up against the dock and the air bags would start filling up again.

 

They don't have to be set up that way. Alternatively, you can have them on individual manually switched solenoids wired to the dash.

 

Dumping the rear might be easier if the trailer is empty or really light. Dumping the back with a 45,000lb coil parked in the middle of the trailer could be interesting.