These instructions are based on my experience implementing the already posted solutions on Miata.net. I took the opportunity to take pictures to clarify the process. I just purchased my 99 Miata, and at purchase time the dash was already sagging at 40k miles. Having done my research I knew this was correctable.

The process involves the lower half of the dash, it's basically open plastic bolted on in 3-4 spots. Figure 1 shows the original condition, the sag should always occur to the left. Directly under the glove box is a metal support. This is attached by 2 small screws and one larger one. Figures 2 and 3 show the mounting screws. The two black ones (one has already been removed in the image) hold the plastic on, while the bronze screw actually holds the support to the frame. This is the important one. Remove the two black screws, then carefully remove the bronze one. This one should be a lot tighter, be careful not to strip it. With the support removed the lower part of the dash will be a lot more pliable. What we are trying to accomplish is shown in figure 4, the right lower part of the dash must be pulled out and down. In this figure I am pulling this out to show how it solves the problem.

The first step is to expand the hole used by the brass screw. You must extend it back towards the front of the car, Figure 5 shows this change completed. Notice how the outlined hole is ovalized, not round. This image shows the modification completed. This will allow you to move the bracket forward, but to move it down, you must put spacers between the brace and the frame it attaches to. Figure 6 shows the screw in place, I have some washers used as spacers on the other side of the brace, but they are hard to see in the image.

Now, put the brace back into place, you may want to loosely screw the left side black screw on to hold the brace while you work on the right. You'll need to put enough washers there to hold the brace down enough to level the dash, you may need to try a few combinations to make it work. Also, remember that you'll want to take advantage of the additional space you made in the screw hole to move the brace forward. Once you think you've got it right, tighten up all the screws and see how it looks. The black screws tighten into plastic so they are only lightly tightened, but the brass one needs to be very tight. If this one comes loose the dash will shift back and cause a sag again. Figure 7 shows the final result.

Based on the design, it's possible that the main screw will come loose or additional sagging will occur. The brash screw is a philips head, I'd recommend replacing it with a good hex head that can be properly tightened without a risk of stripping. I haven't had the opportunity yet, and probably won't until this comes loose or needs more adjustment.

That's it, you're all done.

James
james.carroll@clearorbit.com
99 Miata LS
02 Golf GLS TDI
93 Honda VFR 750

Note from Dennis FitzGerald

Like some others, my NB's glovebox sagged on the left. See Figure 1 of James Caroll's suggested fix, found at the miata.net Garage/Interior link. I removed those 3 screws that hold the metal support strap.

While doing this I noted that the glove "box", the actual black plastic bin, was fastened to the glovebox door (the outside cover that you see when the glovebox is closed) at the top left and right as well as along the bottom. After noting this I also noted that the top left side the "box" and door was not at the same thickness (bin and door near the screw) compared to the right side. For ease of disassembly I totally removed the glovebox from the car. Simple to do as it is kept in place by the pivots that are supported/strengthened by the now removed strap and the limit 'ears' that keep the glove box from opening too far.

With the assembly on my lap,I removed those 2 top screws. Looking through the screw hole there were 3 different colours of plastic, the black of the bin, the interior colour door (beige in my case but black for others) and in between was something white.

It turns out that the white 'something' are a few plastic shims. I removed 2 of these shims from the top left, reassembled everything and my glove box is now square. Why there were more shims on the left than the right I have no clue but it was a very simple 10 minute exercise using a Phillip's screwdriver. Perhaps this 'fix' will work for others.