Securing Your Rocker Panel Trim, Proactively

(Rocker panel trim is the painted plastic body trim underneath the doors)

Rocker Panel advised mod1

courtesy of Long Road Racing; click to enlarge

Quite a while ago, I recall reading how those that were auto-crossing and racing their Miatas and perhaps coming in contact with those pesky orange cones, were losing their rocker panel trim (commonly, but technically incorrect, called rocker panels) and how Mazda had responded by issuing a TSB (Global MX-5 Cup Car Technical Service Bulletin #3-22-17B), which not only answered these driver’s concerns that the panels were just hanging on plastic clips, and therefore, weren’t really “fastened” to the vehicles, but it also made fastening the panels a “legal” modification for racing qualification (I’m curious as to whether Fiat has issued a similar TSB).

I recall reading the TSB, and not having a very good idea as to where the three self-tapping screws were allowed, nor where the mounting surfaces were and what these clips looked like (I didn’t try very hard, as I haven’t looked underneath there since installing the plugs my dealer forgot to install).  Then yesterday, someone posted a common forum question – “What are these plugs for, and what do I do with them?”, and with one of the replies, a very clear photo showing the clips that hold the rocker panel trim, was posted. 

chassis plug

photo courtesy of Casey Jones

Now it became clear, that dislodging the panels probably wouldn’t take too much force.  I’ve been told that driving through an unexpected large puddle at highway speed could be all it takes!

I brightened up another forum photo showing a screw in place, and it too reveals the clipping better

Rocker Panel advised mod

source unknown

So even though I’m not an Auto-crosser, I think I’ve finally been inspired enough to locate some quality stainless steel self-tapping screws, to insure that some road debris won’t dislodge one of my rocker panels, by pre-drilling and installing at least 3 of those screws per panel (if you aren’t qualifying for racing, 5 might be better), along the inboard edge in the vicinity of those bottom clips, where I’m confident the actual rocker panel sheet metal is directly behind the trim.  This will prevent the panel from “shifting” out of those clips, or falling off should some of them fail under stress, as magoffin’s have.

rocker panel clip failure

photo courtesy of magoffin

It turns out that you needn’t raise the car that much to drill the holes.  Lifting the vehicle at the forward rail “pad” such that the suspended front wheel is about an inch off the ground, was plenty high enough for both drilling and driving the screws in.


About an hour after I published this article, Leon Russ posted this photo , along with his comment that road debris had just dislocated his rocker panel.  This is exactly what I wish to avoid!

rocker panel off

photo courtesy of Leon Russ

Looks like there are about 10 other green clips holding the trim panel on, in addition to the 5 white clips along the bottom edge. 

If your rocker panel does become dislodged, Tim Oyer had this advice for reinstalling:

Take all the green clips out of the body of the car (just take something thin and fairly rigid and squeeze in one side of the squeeze-clip, then gently rotate and yank it out), and put them in place on the rocker panel. Once all in place, slide the bottom clips into place, then rock the rocker upward and push the green clips into the mounting holes. It can be done easier if you lift the car up a bit, but otherwise can be done in a parking lot, no problem.  When you get home, add the screws!

14 thoughts on “Securing Your Rocker Panel Trim, Proactively

    • I would say whatever you can find about a ½ inch long 😉

      Looks like Glenn Long used a power tool to drive the screws in without setting the torque down, and deformed the plastic somewhat. Probably better to pre-drill and use a regular screwdriver?

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  1. Just did this with some number 10 stainless self tappers. I suggest drilling a small pilot hole. Makes it much easier. That is some tough steel! I don’t autocross but looked like a simple preemptive mod. Previous example would be a bad day!

    Liked by 1 person

    • Thank you Dan. I haven’t gotten around to it yet. Were you able to do this with the vehicle on the ground? or lifted up somewhat? Not thinking I’ll be able to do it without getting the car out in some lot and jacking it up, is what is holding me back, as I have a tiny one-car garage.

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      • Used a floor jack and raised it a few inches to be able to get the drill under there. Plus to see better.
        Read somewhere else that someone was concerned what was behind the metal. I pulled the sills off and there are slots under there that you can see into the channel. It is completely empty. The wire harness runs the length of the sills [further inboard] on both sides. That put my heart at ease!

        Liked by 2 people

  2. danotech63 – when you say the wire harness runs the length of the sills, is it in the channel? Or does the harness run alongside the channel? If it’s in the channel and the self tapping screws and harness start to rub on each other, that could cause some bad results.

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  3. If you enlarge the first photo, you’ll see specifically where along the outboard edge, the placement of the screws is recommended by Mazda. There should be no concern of hitting wiring, unless you choose different locations. I haven’t inspected closer though, as danotech63 has.

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  4. danotech63,
    Reading your June 11th comment again, I realized that these trim panels aren’t technically “rocker panels”, and that the difficulty you had pre-drilling the holes, since “self-tapping” screws weren’t grabbing, was because high-strength steel is used in the actual rocker panels.

    On unibody automobiles where the body and frame of the vehicle are one, rocker panels provide the structural reinforcement that keeps the bottom of the vehicle from sagging in the middle. On more modern cars and trucks designed with front and rear crumple zones, the high strength of rocker panels is essential in creating a passenger cabin area that does not deform in an accident the way hood and trunk sections are designed to. more details on – https://www.carid.com/articles/rocker-panels.html

    I revised my article title accordingly.

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  5. Wondering if the method described in the TSB is a good idea for road vehicles.
    That looks like a rather exposed area and with driving a screw into the body you might end up with a rust problem later. From the pictures it doesn’t seem that one has access to the far side so that one could seal the hole.

    What about drilling into the grey plastic clip and tightening the ‘panel’ with a washer? Even if that doesn’t prevent it from becoming dislodged it should at least not fall off. In theory that is…

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    • Tobias, I’m not a BIW expert, but rocker panels are generally more prone to rust than any other area of the car. Because trim is used to cover that area nowadays, you won’t normally see that rust until it is so bad, the trim can no longer remain in place. None of the holes for the 15 clips in the article’s last photo are sealed, so I’m afraid I don’t share your concern for these additional holes.

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      • Dan, you’re right.
        However the area behind the trim seems to be painted so there hopefully also is paint around the holes and their edges which should prevent rust from forming from the outside.
        A hole drilled after painting wouldn’t have any protection. I think that with the TSB method the rust risk might indeed be higher.

        Water getting past the clips and forming rust on the inside is a different issue though, and as you said, 2 further holes won’t make a difference. I hope that Mazda has also thought of this 😉

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  6. I faced the “flying rocker panel” problem on my ND a few months ago, i got stuck on the mud on the side of the road, the panel made contact with the ground and got loose (ooops, my fault).
    On the ND its fixed by 10 green clips on the top (D10E51SJ3), 5 grey clips on the bottom (BP4L51SJ3) and another one inside the front wheel arch (BGV456145).
    While waiting for the parts to arrive, i drove several weeks without it, taking the precaution to cover the holes with tape. [sentence edited]

    Hope this helps someone 😉

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  7. I finally did this project on my own vehicle today 😉

    You sure need a high quality, sharp drill bit for that high-strength steel! I don’t plan on driving through any mud, but regardless, now I’ll feel confident that a surprise large puddle won’t sabotage me.

    Liked by 1 person

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