While on the road last month I spotted this tractor-trailer being backed into a parking space in a shopping mall in eastern Indiana. I noticed that the trailer, a Mac, was equipped not with the usual fixed tandem but with a lift axle. It was raised because the pneumatic tank was empty.

Liftable axles are nothing new, but it seems like there are more of them forming part of the tandem on trailers. I shot some photos, then went to talk with the driver, and learned there was more to the trailer than the axle. 

He said his company hauls powdered cement from Kentucky to concrete producers around Indianapolis, and has a number of trailers with these axles. “Do they pull differently than a standard tandem?” I asked.

“Yeah, they track better when the axle’s up,” he said. “And they turn corners easier,” because the tires on the single lowered axle don’t have to fight the ones on the other axle when it’s down.

I also noticed that this tanker lacked the usual forward fenders that protect the tank body from splash and debris kicked up by the tractor’s tandem. Full fenders on the tractor made the trailer fenders redundant, so they had been removed.

Air Products & Chemicals in Pennsylvania had gone this route to conserve fuel. The tanker fenders acted like sails, the manager said, catching wind at highway speeds and creating drag.

This driver said a few of the company’s trailers had gotten the fender-removal treatment, and yes, they did seem to pull easier and save a little fuel. The tractor’s reinforced plastic fenders are lighter than the aluminum ones on the trailer, so the rig ends up a little lighter, too. Every little bit helps.

A fleet making such a changeover would have to put fenders on most of its tractors before removing fenders from the trailers, of course. But it seems worth the effort.  

The driver also pointed out the shrouding that encloses part of the hopper mechanisms and around the ladder in the rear, which further smooths air flow. Tires are protected with a pressure monitoring and inflations system. And the ladder's mounting angle makes it more of a stairway, and the handrails add safety. A lot of progressive thought has gone into this trailer!