Frame Rail Installation

Place the car safely on jackstands, far enough to the ends of the rails so they don't interfere with rail installation. Remove the plastic door sills (gently lift up), then unhook the carpet.

Unbolt the seat belts.

Remove the plastic carpet fasteners behind the seats.

Unbolt the seats. If you haven't unbolted them before, they can be very tight. You may opt to use a breaker bar, but I'd also recommend using 6-point sockets only to ensure the bolts don't get rounded here.

With the seats out, you're now ready to lift the carpet. Place an empty cardboard box or something to lift the carpet off the floor to protect it from drilling. This is also a great time to vacuum the floors and underneath as well!

If your stock rails are bent, time to get them straightened out enough for your new frame rails to fit. Mine weren't horrible, so I used an allen key to pull the metal out, and used a C-clamp to press the rails into shape. Yes, the frame rails are that weak, that I can use cheap floorboard samples to straighten it out (samples free, courtesy of your local hardware store).

This is a "cheat" shot, but you want to test the frame rail fitting. Place them as far up as possible, while keeping them flat against the floorboard. If not placed far up enough, the rear bolt holes may lead you to drill past the accessible floor board area in the rear. Once the fitting looks good, I used a jack to lightly press frame rails into place.

Once the frame is in place, use the rails as a guide to drill the 3/8" holes through the floorboard.

Once the holes are drilled, install the bolts. I used a bit of LocTite blue on each bolt. I installed them all loosely, preferring to tighten them all up once the all of my brackets were in place.

The fuel lines are managed by metal brackets. The Flyin' Miata instructions have these installed on a bolt at the bottom of the frame rail. To preserve ground clearance, I decided to install the brackets on the inner bolts of the frame rails.

First, start by straightening out the bracket. The metal brackets are pretty soft. I just took some pliers and pushed it against the ground to straighten them out.

Example of a straightened bracket.

Take the same 3/8" drill bit and extend the existing bracket holes. The holes are almost the right size, so there's very little to cut out.

I wanted the extra bracket to put a total of 3 at the front, middle and back. There's an extra black plastic bracket held in by a 10mm bolt by the fuel filter, underneath the plastic shield. It's just before the right rear tire. You may find a white plastic bracket towards the front, but it has a slightly different layout for holding the metal lines.

Brackets are in place and the fuel lines are safely tucked against the inner frame rail. Bolts are now completely tightened. Undercoating was applied over the bolts.

Undercoating was placed over the top of the bolts.