I recently got a Rubicon front bumper from a friend for my JK X model. I installed it last Friday night. In doing so I broke every last one of the plastic retainers that hold on the plastic belly pan thing. My question is there any reason to replace this plastic pan other than looks.

 

Many have taken it off..including myself. Other say it was designed to create air pressure. I say it was built for looks cause "normal" people don't want to see everything under the Jeep. Some debate on a "gas savings" difference.

https://www.jk-forum.com/forums/stock-jk-tech-12/air-dam-1603/

 

What's the diference between a Rubi and an X front bumper?
As for the plastic piece under the front bumper, mines been off for the past 2 years, when I replaced the stock bumper with an AEV. Havn't noticed any diference. I did mount a small extruded aluminum piece on the bottom rear of the bumper to keep out all the leaves and crap from getting into the radiator cavity.

 

could have the silver insert or the fog light cutouts?

 

My X bumper did not have Tow hooks, nor did it have the Fog Light holes. I really wanted the bumper for the fog lights and the tow hooks, but later found out that the fog light were not going to be plug and play, so I decided to just mount the tow hooks, cut out the holes in my bumper and use my bumper skin, That did not go as planned, Turns out the inside mold of the bumper off my X was not countored to accept the tow hooks, I did not find this out till after I spent some time carefully templating the stock holes off the Rubi bumper cutting them into my X bumper only to find that the tow hooks would not fit between the inner steel bumper and the outer plastic bumper cover, So I ended up mounting the Rubi bumper, with he tow hooks, and Looking for something to fill the Fog light holes. If anyone has the same problem, I found a set of 5" heater duct defusers @ home depot that hold into the fog light holes perfectly with a set of three spring loaded clips. I painted them flat black with Kryole patio furnature paint and they look awsome. Just to be safe i hooked some small bungies onto them and onto the lower radiator support and they look factory. I will try to get some photo's to post.

 

I took mine off when I put on my rubi bumper, (cut the clips right off as they were such a pain in the butt to remove). I had it off for a couple of weeks and decided that any protection on the bottom is better than nothing so I put it back on.

I ended up just getting some stainless nuts, bolts and washers from home depot for abound $6 and now I don't ever have to deal w/ those plastic false screws ever again.

As far as the practical use of the lower plastic piece I think it performs a 3 fold purpose (though all will not agree with me).
1. Protection from light rubbing on the front end.
2. Help provide a smoother surface to start the air flow underneath the jeep (maybe help mileage just a little bit)
3. Create low pressure behind the radiator allowing for more efficient cooling.

I do like the look of the jeep w/o it but I tend to be a function over form guy and that piece even though I'm not too keen of form I do appreciate it for function so on the Jeep it stays.

Hope that helps.

 

Some people (me included) also believe that it helps to reduce hood flutter.

 

I can tell you this, regardless of what it was DESIGNED for, it's easily the first thing "trail modded" on most jeeps. (Read: Ripped off on terrain)

 

It does not cut down the hood flutter at all.. it is the same weather it is there or not

 

i'm thinking aerodynamics but i can't see it really helping something that already has dynamics of a "TOASTER OVEN"