San Diego Miata Club

Installing an Autopower Roll Bar in Your NA or NB

Submitted by Ted Kesler


These are the easiest to install of all the Miata roll bars. Even so, the job takes two people and six to eight hours the first time. In addition to the roll bar and mandatory SFI 45.1 padding, you will need the usual automotive metric tools, jack stands, a large fork, a grinder, tin snips or sheet metal nibbler, a drill and bits, spray paint or rubberized undercoating spray, Loctite, and Band-Aids.


Please read this over carefully before you start your installation.

Preparation and Disassembly

  1. Block the front wheels fore and aft. Jack up the rear of the car and find the notches in the rocker panel weld flange just ahead of the rear wheel opening. There is a corrugated pad just inside the notches. Place jack stands under that pad, not on the weld flange. A small piece of thin wood or rubber between the stand and body is a nice professional touch.
  2. Remove the rear wheels and the plastic inner fender covers at the front of the rear wheel openings. The rear pads of the roll bar will be bolted through the body here.
  3. Remove both seats. There are four bolts through the floor on all Miata seats, and they are really tight. A long socket extension will help give you room to apply the force needed to break them loose. Some cars have additional seat belt anchors into the transmission tunnel. There may also be wiring to disconnect under the seat.
  4. Note: Cover the center console to prevent scratches; a blanket on the trunk lid makes a handy tool/parts shelf.

  5. Remove the piece of carpet behind the seats. Remove the fasteners from the carpet on the package shelf, and roll the carpet and rubber pad back under the window. A meat fork works well to pull the carpet buttons, and a piece of wood about 18 inches long will help prop the convertible top up out of the way after you roll the carpet back.
  6. Remove the black metal piece at the top of the doorjamb, and pull up on the rubber edge that runs down to the doorsill. It will pop right out. You may need to loosen the rear screw in the sill plate to replace this rubber edge later.
  7. Remove the seat belt swivel cover. They are a friction fit and quite fragile. Pulling up gently with your fingers works best.
  8. Unbolt the seatbelt swivel. Note the amount of free play in the swivel before you remove the bolt. You will need to reassemble the swivel with the same amount of free play. Keep the various spacers together and in order (the bottom of the bolt should have a white plastic retainer collar). Lay that assembly over the front of the tower.
  9. Remove the fasteners from the plastic cover on the seat belt towers. The plastic button on the side has a center piece that will release the button when gently pulled out a bit.
  10. Release the plastic tower cover. Insert your hand between the plastic and the body about halfway down (where the rubber edge in step 5 was) and push the plastic inward, towards the center of the car. It will make a mighty pop as the spring fastener inside releases. Note the plastic alignment spud near the spring is at an angle. The cover does not go back straight on.
  11. Fish the seatbelt out of the tower cover. There is a rectangular plastic piece that stays on the belt. There is also a small plastic piece holding the top together. This part usually breaks about now, but you will probably trim it away later anyway.
  12. Unbolt the seatbelt reel. It has a screw on the top and a bolt on the bottom, and is filthy. There is a plastic bag in there that helps keep everything together. Notice how the belt twists and comes up, over, and down; you will need to put it back the same way. Lay the belt assembly on the floor of the car.
  13. Remove the curved sheet metal package shelf. Do not remove the separate flat panel — it covers the fuel gauge wiring on the top of the gas tank. Remove the heavy felt pieces beside the gas tank by grabbing the really sticky two-sided tape underneath and lifting the whole mess straight up.

Fit and Install the Roll Bar

The next few steps are the core of this job and require two people. You may have the bar in and out several times. Be gentle with the wires in the area.


Note: This part will involve cutting and drilling within inches of the gas tank. Think about that often! A stray drill or grinder could be serious business. Don't rush and take your time.


  1. Trial-fit the roll bar. The vertical bolts at the bottom of the main hoop go into existing holes in the seatbelt towers. The adjacent vertical flange fits flush against the rear face of the tower. The rear legs sit on the deck beside the gas tank. This is a two-person job. Even so, you will usually scratch the bar, but below the carpet level. Don't pinch, stretch, or break the stray wires in the area.
  2. Trim just enough metal from the roll bar flanges to position the bar. Usually, just a bit on the body-flange alongside the legs is enough. Sometimes, the flange just behind the leg must also be trimmed. A grinder or nibbler works well here; the material is too heavy for snips.
  3. Note: The front corner of the pad on the right leg usually touches the wiring harness where it goes through the deck. Trim the pad (and backing plate) to clear the harness and grommet. You can't bolt through there anyway.

    Note: The pads and backing plates come with only three holes. You may have had to cut off one of the holes while trimming for the wiring harness, so you may need to add the third hole at the back of the right pad. This backing plate may also need to be narrowed slightly to fit against the gas tank. Some people add a fourth hole in the left pad and backing plate. This is your call.

    By now you may have tried and failed with your Dremel. It is not the tool for this job. You really do need a grinder here and/or a nibbler later. Harbor Freight has a tasty 4.5 inch grinder that you will find hundreds of uses for after this job. It has been on sale for about five years now. Check it out. If Harbor Freight is not for you, we can relate. But you still need a grinder for this job.

  4. With the bar firmly in place, all the way down in the seat belt towers and rear deck:
    1. Drill a pilot hole down through the deck, using the hole in the front of each rear leg pad that your drill allows easiest access to. A small bit at the angle you can manage is ok. This is just a pilot hole. Some use a really long bit or an angle drill. If you like perfect holes and match-ups, this part will drive you crazy.
    2. Drill up through the pilot hole from the bottom with your finish size bit. You may have to root around some to match with the pad hole above. This is fine; this first hole is usually ugly.
    3. Bolt up the backing plate in the first hole, eyeball it into position, and drill another hole. Bolt through this one, repeat, and the third hole will be a perfect fit.
    4. A messy option is to spray or undercoat the deck above and below now (step 2.5), and "wet mount" the pads and backing plates. This is your call.
    5. Bolt up the entire bar finger tight. Then fully tighten the bar, in this order: The tower vertical bolts, the tower horizontal bolts, then the pad bolts. Loctite is a great idea for all roll bar bolts.

    Note: The bolts down into the top of the seatbelt tower will require a delicate touch and small hands. You have to install a washer and the nut up inside the tower. Fun! A fender washer (a large diameter washer to spread the load better inside the tower), which may not have been supplied with your bar, is a good addition at this point.

    The horizontal bolts in the same location are easier, but if they don't quite line up, a little crow bar action may be required. Slip the bolt in from the back, with a washer and nut inside the tower.

  5. Spray paint or undercoat the backing plates, exposed nuts and surrounding area under the car. Replace the plastic inner fenders and attach the wheels.

Reassembly

The next few steps make or break the job visually. The package shelf will be hidden, but working with the thin, sharp-edged sheet metal is not fun. The carpet fit—and especially the seat belt tower cover fit—will be a source of pride or consternation forever. This is not the time to rush to finish up. Take your time. If it's getting late, this is a good place to knock off for the day.


  1. Trial-fit and trim the package shelf sheet metal. Tilt it down on one side, and all the way back, then eyeball and mark the area to be removed. Snip away! Fit, mark, and snip the other side. (Instead, you can make a paper pattern and do a real pretty job. Either way, this will all be invisible under the carpet.) Vacuum out all of the chips and grinder dust. Trim the felt pieces to fit around the bar legs and replace them. Replace the shelf.
  2. Replace all of the carpet. Trimming the hole for the bar can be done now or later, or by a professional. This is your call.
  3. Hint: Make a paper template of the hole location relative to the edge of the carpet, and mark the cut from that. The hole will not be round! Whacking away at the carpet right now can be disastrous. Don't ask how many shredded messes I've seen from hurrying to finish at this point. You're going see this area every time you get in the car. Your significant other is going see it every time, too! Take your time.

  4. Replace the seat belt reel in the tower. Take your time; it's not as simple as it might look.
  5. Trim and replace the plastic tower cover (Refer to step 3.2). This step is a wrestling match with the seat belt, the little rectangular plastic part around the belt, the seatbelt bolt spacers (step 3.5) and the cover itself. This is also going to show every time you get near the car. There is no template available, nor is one necessary. Fit and mark, then cut, file, snip, or Dremel (yes, here there is a use for one—just don't melt the plastic). Take your time and plan ahead; this can also be done tomorrow. When you have trimmed to suit yourself, position the cover via the locating spud and the spring fastener (step 1.9), and smack it back into place with your hand or a rubber mallet. A drop of oil on the spring may help. Do this when you are done, not every time you check fit the part. These covers are not cheap, but they are fragile! Replace the other two fasteners.
  6. Replace the seatbelt swivel. Mix and match the spacers as needed until the swivel just clears the top of the plastic and still swivels. You did account for the spacer diameter (step 3.4) in your trimming, didn't you? It's a different fit now due to the roll bar base plate. The spacers only go to the plate now, not down into the tower. Check the seatbelt for extension, retraction, and swivel. If you didn't break them earlier, replace the swivel covers.
  7. Replace the rubber cover strip and the metal doorjamb top (step 1.5).
  8. Install SFI 45.1 roll bar padding. Trial-fit and mark the position, then peel off the covering on the adhesive backing and press the pad onto the bar. Zip ties add that racer look.
  9. Hint: The SFI 45.1 pre-formed padding from Hard Dog fits Autopower bars perfectly. Buy the bar and the padding from Brian at Good-Win Racing!

    Do not drive or ride in a Miata with an unpadded roll bar. Yes, you are tall enough for your head to hit the bar. You’ve come this far OK, don’t waver now.

  10. Replace the seats. Don’t forget the wires underneath.
  11. Remove the jack stands, lower the car, and torque the lug nuts.

If it is still light outside, go for a ride and enjoy your new toy.


Disclaimer

Please note that these tips and pointers are not reviewed or approved by Mazda Motor Corporation or any other corporation or entity other than the originator. The San Diego Miata Club does not accept any liability for damage or injury as a result of utilizing these tips and pointers. Please use common sense and always remember safety first.


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