Long panels below trailers reduce windrag?

I think they put those there so all the rice burner cars would stop trying to pass by going underneath the trailer!

 

it's part of an "aero package" to lower drag and improve fuel economy.

 

That's the general idea... not sure how effective they are though; it was introduced through a government fiat out in California. I might see 0.2 to 0.5 mpg decrease in fuel consumption. Going to low rolling resistance tires is more effective.

 

My guess is that some politician has an interest in a company that makes these and decided that it would be a great idea to mandate them since noone was buying them.

 

Low rolling resistance tires (super singles) are dangerous in snow and rain because they don't get enough traction.
The side skirts do help, according to a Prime driver I was talking to at Quantico a few weeks ago. My company is starting to get them due to the fact those idiots won't quit booking loads to the Peoples Republik of California. I've heard they make a trailer harder to handle in a crosswind. But of course, the boss disagrees.

 

Yeah they probably help .0000000000000000000000123% on the fuel milage......(that is) while they manage to stay attached to the trailer.

How is creating millions of huge plastic panels (made from petroleum) that fall off and litter the roads or the landfills, how is that saving the environment?

 

I don't know. I don't like them. I've only pulled those trailers twice, and in the summer, and loaded. But I hear they're terrible in a crosswind when empty or light, and in winter they accumulate lots of snow and you have to kick the #### out of them every time you stop or you'll eventually build up enough weight to have problems at a DOT scale.

About a year ago I asked the vice pres at my company if we're ever going to get the belly skirts on our trailers and he said "No, that's just one more thing for you guys to F*** up.". Now all their new trailers have them because of the California law.

 

I'll disagree with you too - I hear these stories all the time... "You'll be sorry!" Well I'm not. I've been running wide singles, and a number of times last winter I had better traction (running both heavy and empty) than the guys with the duals. Up in VT, 3' of snow in 24 hours... at least a dozen trucks equipped with duals stuck in the snow or jack knifed. I didn't have a bit of problem getting to where I wanted to be on wide singles.

As to this, I've never had a problem with ice/snow build-up on side skirts. It just doesn't happen.

How they are constructed is important. Some of the junk that just bolts some metal or plywood onto the side of the trailer is going to get damaged. The product installed by Utility works very well... they are mounted using spring steel brackets that "give" quite a bit. I believe the skirt material is kevlar. For example, going into and out of a sunken dock, the spring brackets allow the skirts to splay outward, and the kevlar material just wears down a little as it slides across the pavement.

 

I haven't pulled a belly-skirt in snow yet but unlessthey're wax-coated or something, they'll collect snow and ice. Trust me. Snow and ice will build up on ANYTHING down there. I'm talking about the spring-loaded hardware behind the panels that you can only see when you look in from by the front of the tandems. Do you haul heavy loads? I haul meat loads, always over 40k, so snow load is always an issue to keep in mind.

As for the super-singles, I ran them two winters. I never had any problem with the racing slicks on the trailers, but on the tractor they were TERRIBLE. #### truck would start fish-tailing fully loaded when there's barely any snow on the road. Maybe it's the particular brand/model of tires we had that sucked because I hear guys on the CB all the time .. some guys agree with me, others say they're great. And I've seen them on tankers. What I'm saying is the 4 wide-based tires I had on that 2007 Volvo were TERRIBLE in snow and heavy rain. I got out of that truck and got into a 2008 Volvo with conventional tires and the #### truck got better traction in snow EMPTY than the super-singles truck did fully loaded. My company tried out the super singles for a while. 40 trucks and 50 trailers, I think. Drivers raised hell about them and they went back to conventionals. I think all but one of the super-single tractors have been traded off, but we still have a few trailers with them.