S4 Side Skirt Intall(Undercarriage Screw Length?)

**tmaclax013** · 03-10-2016 04:21 PM

So I recently picked up some color matched, brilliant black side skirts to put on my A4. I got all the mounting figured out, torx bolts inside front and rear fenders, velcro on the inside, etc. My question is, when securing the lower flappy part of the side skirt to the undercarriage what did you guys use? The general consensus seems to be self tapping screws. If thats what everybody has used then my only question is, what length screws are the most ideal? If you guys used something different let me know, Im open to ideas.

**MetalMan** · 03-10-2016 04:51 PM

Interested too... the previous owner of my skirts "pre-modified" them for the A4, which included removal of some of the "lower flappy part" so my only option is to use self-tapping screws to the undercarriage.

**tmaclax013** · 03-10-2016 04:52 PM

I see you like my terminology haha

**tar** · 03-10-2016 05:31 PM

I'll check mine ina few. The avants are held on with what look like drywall screws and sag very very badly. Sedans look perfect so I'll be going off those for you guys

**OverSpun** · 03-10-2016 06:06 PM

I think my fender trims are riveted on (S4's trims are factory riveted on anyway). I had my bodyshop put them on while I had some paint work done.

**tmaclax013** · 03-11-2016 08:12 AM

@Tar thanks for checkin it out. Im probably going to end up with like 1/2" self tapping screws and use some big washers to screw throught the factory holes on the side skirts. I just obviously dont want to screw into the floor of the cabin. that would be tragic

**ElSabio182** · 03-11-2016 08:16 AM

Half-inch or 3/4 inch self-tappers is what I used, either should be fine. Use a big-ass washer to help distribute the load on the plastic flap so it doesn't tear through it. I used 2 screws per side. Make sure both the screw and the washer are stainless! Not a terrible idea to try putting some sort of sealant on/around the screw hole as best you can to keep water/rust out of there.

I considered using rivets, but I wasn't sure how thick the "floor" with all that rubber undercoating was...wasn't sure if an at-home pop rivet would be "tall" enough.

**AudiSport12** · 03-11-2016 08:36 AM

^ What he said. 3/4" and use a large washer. I did 3 screws per side.

**tar** · 03-11-2016 09:05 AM

Mine are 3/4 with washers and I have 4x per side

**RagtagXMASTER** · 03-11-2016 10:38 AM

So we all used 3/4 and large washers. I used 5 per side

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**demonmk2** · 03-11-2016 10:40 AM

Can also use threaded rivets to basically bolt it to the under carriage
I did this and has held up for 3 years and it's clean looking
You can pickup a kit at haborfrieght

**MetalMan** · 03-11-2016 10:58 AM

Originally Posted by demonmk2

Can also use threaded rivets to basically bolt it to the under carriage
I did this and has held up for 3 years and it's clean looking
You can pickup a kit at haborfrieght

This sounds like a good idea. Do you recall what sized threaded rivet you used?

**ElSabio182** · 03-11-2016 01:35 PM

Yup, I considered doing riv-nuts or whatever...but again, I wasn't sure how "deep/tall" the rivets needed to be, so I said fuck it and did the screws. Didn't feel great about it at the time, but they've held up! Although apparently I'm the only one using just 2 screws

**tmaclax013** · 03-11-2016 02:48 PM

Yeh Ive contemplated using nutserts for a couple things but they always turned out to be much more of a hassle than theyre worth. Think ill be going with 3/4" stainless self tapping screws, seems to be the general consensus. It seems pretty obvious but just to make sure... NOBODY HAS HAD ISSUES WITH 3/4" poking through the floor or damaging electronics correct?

**demonmk2** · 03-12-2016 05:38 AM

Originally Posted by MetalMan

This sounds like a good idea. Do you recall what sized threaded rivet you used?

It was either 8mm or 10mm ( 1\2" in length I think ) I can't remember. It was in the kit I bought from harbor freight. You'll have to buy the bolts\washers separate though,
It's cheap too. I put permatex on the bolts and tightened them down and have held since.

**tmaclax013** · 03-12-2016 07:49 AM

You have to drill a hole in the undercarriage to use the nutserts correct?

**RagtagXMASTER** · 03-12-2016 09:49 AM

Our cars have pretty much a sub floor. When you put your self tapers in aim for the square chanel under the car its like 2 inches tall for your bumper shocks. I put my screws in that line to avoid all issues with electronics and it is not hard. You could used 1.5 inchers probably and have no issues there.

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