So I've rounded up a plastic undertray to replace the one that was missing from my FD when I got it. What kind of fasteners did Mazda use to attach the undertray to the bumper along the front edge? Also, same question applies with regards to what they used to fasten the bumper to the Air guide piece. See pictures for reference. My guess is they used plastic clips or maybe M6 U-nuts and bolts.



Here's a shot of the front of the undertray & bumper - am I correct in assuming the undertray goes BELOW the bumper skin?

Here's a shot of where the bumper mates up with the plastic Air Guide piece

 

Undertray to bumper: Metal U-nuts mounted to the bumper and then flange bolts from the bottom. Undertray mounts below the bumper.

Bumper to Air guide is three plastic clips, NA0150101A. If you Google that part number you'll see several pictures of it, its a unique shape.

 

The front edge of the cover attaches below the bumper and air dam with 6 bolts that go into U or speed nuts, plus a plastic clip near the center of the front. The U nuts should be captive in the bumper. There are 6 more bolts that are of the same diameter and thread, but a bit longer. They attach the cover at the sides and rear middle. There are 2 more plastic clips at the rear corners. I think these 3 plastic clips are intended to hold the cover in place while it is being secured with the 12 bolts. [In the second photo, the inside of the cover is shown. The front of the cover is up in the photo.]

 

from the pic, the green arrow is BR70-50-0Z2 they have the funny shank you can see in the pic
Red arrow is 9072-00-616 which is a 6x1.0x16mm bolt
the plastic clips are 9926-50-625 not sure what they look like they go missing a lot, nut and bolt work too

 

I have used these bolts for ages -

https://www.clipsandfasteners.com/M6...s-p/a13618.htm

They work awesome for the under tray, nice big captive washers and the end is a point that helps get it started with rusty bolt holes. They hold up well over time too.

That whole site is a gold mine of fasteners BTW and great pricing.

They probably have a U-nut of some kind that would work as well.

Dale

 

I followed j9fd3s's arrow colors to show where the longer bolts (green) and shorter bolts (red) are used. The 6 longer bolts are shoulder bolts -- they have a short, larger diameter unthreaded shoulder on their shaft just below the head that acts as a bearing surface or spacer so that they don't crush the plastic surrounding their holes in the under-cover when they are fully tightened. The shoulder bolts also allow the cover to flex and move around a bit, unlike conventional bolts.

Positions of the 3 plastic clips shown by the yellow arrows:

 

Thanks for all the responses guys! I had a bunch of spare M6 U-nuts and regular M6 bolts laying around in the shop from my FC that fit the FD fine, so I'm good for now. Looks like I'll be ordering the specialized stuff from clipsandfasteners.com for a more permanent solution.

 

By chance were they the same bolts and nuts that hold FC's front bumper?

 

some of them, the FC doesn't use the fasteners with the shoulder, it just uses the bolt and washer style in two lengths, why?