INCREASE YOUR SUSTAINABILITY/’GREEN PROFILE’ AS A FLEET. If you are an aspiring SmartWay partner, or are trying to meet certain sustainability or reduced emissions goals as a fleet, attacking the trailer mudflap wind drag issues is one of the fastest and cheapest ways to significantly reduce fuel usage.
DON’T RUN WITH EXTRA FLAPS. Tankers, in particular, have a tendency to use both truck flaps with front fender flaps on their tankers. One or the other will usually suffice. Operating with two extra flaps generates at least 1/3 more wind drag on the highway from the flaps. The same is true for flatbeds. If you don’t have to run with extra trailer flaps from a DOT standpoint, then don’t. The extra flaps cost another 2-3% reduction in overall fuel economy for the rig. If trucks have to bobtail at some point, and don’t usually run with flaps, store them securely like you do bad weather chains, behind the rear wall of the cab where they can be accessed and installed on the truck when required.
ELIMINATE ANY KIND OF FLAP STIFFENER. Mudflap wind drag costs enough fuel economy, don’t add insult to injury by trying to keep the flaps from blowing back at highway speeds. These stiffener accessories amplify the parachute effect of each flap, trapping just that much more wind and further reducing highway fuel economy.
DON’T BUILD A ‘WALL’ TO PROTECT LEYMAN (or similar undercarriage) LIFTGATES. Many food distributors operate liftgates that are extremely tempermental when electrical wiring and connectors get exposed to water and road spray. Their home remedy many times is to block the front of the liftgate with a series of solid flaps to redirect water away from the electrical connectors. Several fleets have reported losing 1.0+ MPG when they erected this wall in the undercarriage of the trailer.
DON’T BLOCK THE ICC BAR. The greatest wind drag and turbulence on a Class 8 rig occurs right at the ICC bar. High speed air is flowing through the undercarriage of the trailer, and anything that it slams into at the back of the rig amplifies the reduction of fuel economy. License plates, solid steel plates or struts from the deck to the ICC bar, haz mat signs strung in that same gap, storage boxes and mudflaps are all “no-no’s” that should be avoided if you are spending significant miles on the highway. All of these obstructions pull down fuel economy by 0.3 to 0.4 MPG. If you have to hang something right at the back of the trailer, try to position it so the ‘into the wind’ profile is the smallest possible, and somewhat aerodynamic in shape so it cuts the wind, instead of blocking it.
ELIMINATE ‘COW MATS’. Many drivers like to use extremely heavy and thick ‘cow mats’ as trailer flaps. These don’t blow back in high speed winds, but as a result they lower fuel economy by 0.6 to 0.8 MPG. That fuel bill is an extra $4,000 per year out of your pocket.
REPLACE BAFFLE LIKE HANGERS WITH ANGLE IRON. Don’t use any tricky, solid steel hanger brackets to mount the trailer flaps. All these do is block the high speed air flow on the highway that shoots across the top of your tires. Choose a simple angle iron hanger bracket, and keep it close to the tires – within 5” to 8” directly behind the tires. This is the best aerodynamic spot for any kind of trailer flap.
SHORTEN YOUR FLAPS. Trailer OEMs like to issue new equipment with 30” flaps. (Resellers blithely pass these along, too.) For most box vans and reefers, a 26” or 27” long flap will do. Don’t run around with extra ‘real estate’ blocking wind behind your tires. DOT requires the bottom of flaps mounted directly behind the wheels to be 9” from the ground, which is equal to the bottom of your wheel rim. Also consider lowering your hanger brackets to accommodate a 24” flap. The 24” flap represents 20% less surface area to drag wind. Eco-flaps pull the road spray down and into the flap, so the starting height of the flap can actually be lower than that of a conventional mudflap, and still block more road spray.
