I've noticed today's trucks have this 3-4" plastic guard that runs along the bottom of the front bumper. It strikes me as something that would hinder ground clearance or otherwise brush into things.

What purpose do these serve? Why have they gotten so much bigger recently?

You can see how pronounced it is in the following trucks:

2015 Chevy 2016 Ford

While on these older trucks it is less noticeable, or seemingly even a natural extension of the bumper.

1997 Chevy 1996 Ford

  • 4
    Great question. I always assumed it was aerodynamic or cooling related. Since you mentioned ground clearance, it could indicate the lowest part of the drive train/suspension mount, such that if you scrape it against an obstacle you may scrape a critical component as well. Jun 8, 2016 at 18:52

3 Answers 3


As @MooseLucifer said in the comment, these deflector strips are generally there for air deflection. They do two things - one, they change the air pressure under the car helping stability at speed, and two, they (sometimes) help divert airflow up to the radiator.

In my experience, you always end up leaving it somewhere in the woods by accident.

  • Back in the '80's those were popping up like crazy on cars too. Then later on they redesigned the cars to be aerodynamic without them. A truck is a lot harder to do that... Nov 7, 2019 at 17:39

The more air allowed under a vehicle the greater affect this air will have on fuel economy. The lowered front air deflector will reduce the amount of air and thereby improve fuel economy.

The large over the road trucks have several new air types added in recent years for the same reason. The most noticeable has been the long skirts under the trailers.

  • So even though you're putting a 5" x 40" (or whatever size) hunk of plastic right in front of the air, this is still more fuel efficient than the turbulence that would be had if that air went under the truck instead?
    – Trevor D
    Jun 15, 2016 at 14:27
  • @TrevorD Yes, every air molecule that is excluded from the underside is one that will not have multiple drag interactions with the trunk and road surface. This is why race cars have minimal ground clearance. Jun 15, 2016 at 14:54

It is an appearance extra so the dealer can sell you something ( for pickups) . I added one to my Nissan Titan ; It was an extra offered on the QX 56 suv, so it just bolted to the Titan ( at the time it was not offered on the Titan).

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