Style and Roll Bars

This section of Tips from the Garage is dedicated to the discussion of style and roll bars, their selection, use, appearance and installation. Much of this material is limited by my experience with the subject matter and specific bars. In the future, as the page evolves, it will be augmented by information contained in, and extracted from, the Miata.Net archives, and additional comments and discussion from readers of this page (if you folks respond). Though not as in-depth as you might expect to find in the installation instructions for any specific bar, there will be some good hints and suggestions made for your use. I am always open to suggestions for additional tips that readers might have, so feel free to email me with information that you feel is even the slightest bit valuable. Oh, and please forgive my use of the word "hoop." There just isn't a good moniker for that curved steel tube up behind your head.

Table of contents

Bar Selection
SCCA Requirements
Strength Considerations
Methods of Attachment
Other Safety Considerations - Padding
Installation Stories
Getting the top up and down
Bar Finish
Anticipated Cost
Requested Feedback

Bar Selection

As Miata owners there are a number of reasons why you might be interested in a style/roll bar. Those reasons are the basic criteria you should use in selecting a bar. Once you have determined those basic requirements there are a number of types and designs that you will need to consider, many based on personal preference. Let's start at the beginning.

Why do you want a style/roll bar?
Chances are you either want to equip the car with additional safety features (maybe you're concerned about it being a convertible), need to meet a sports car competition/course requirement, or want to modify (improve?) the looks of the car. Herein lie the primary bases for your selection.

A word of caution at this point, roll bar manufacturers don't usually promise a certifiable finished product, primarily because they can't supervise their bar's installation. Once it leaves their factory, they will usually wash their hands of any liability. If they do make such promises they are asking for trouble. The bottom line is that with whatever additional protection you think your bar might offer (be it style or roll), it is not a justifiable rationale for taking excessive risks. Drive safely.

If you are attempting to meet rules or requirements, there some limitations you must consider. Check out Requirements to get an idea of just what you have waiting for you at the competition technical inspection garage.

Style bars (designed solely for esthetics) include a number of configurations. Those that I am familiar with include a single wide hoop (that covers both driver and passenger), a double-hooped version originally introduced by Racing Beat (the Style Bar II) I believe, and a newer single hoop version that covers just the driver (reminiscent of the old Cobra bar) referred to as Racing Beat's Style Bar III. The latest I am aware of (just stocked by Brainstorm 9/29/95) is a modified version of the Style Bar II. In Brainstorm's version they have modified the ends so they now clear the top frame hinge knuckle to keep it from hitting the bar baseplate on the way up and down. In addition, Brainstorm's design replaced the flat stock baseplate under each hoop with continuous tubing as that currently connecting the two hoops between the seats.

SCCA Requirements

In examining the SCCA Solo I/II rulebook (1994 edition), one finds an extensive listing of requirements in teh Appendix associated with Roll Bars. This is good reading material and provides smart design considerations, but in at least some cases is not followed religiously by the autocross host organizations. In reality, autocross tech requirements are not usually levied against your roll bar, thus it can be almost anything you desire. There are however some organizations that identify that the addition of a bar constitutes a variation from stock characteristics due to its additional stiffening of the chassis. You should check with your local autocrossing organization to ensure that the addition of a bar won't force you to another competition class. Also be aware that the risk of loose hardware is always a concern of the autocross-sponsoring organization and the bar's attachment to the car should be secure. I'll say more about attachment later on.

Solo I requirements are another story altogether and compare closely to the General Competition Rules (GCR) of road racing in the SCCA. Increased height of roll bars are required so that you won't break your neck in a rollover. This is particularly true when used with a racing harnesses (two shoulder belts, a lap belt and a submarine belt). The rationale is that in a rollover, the racing harness will not let you get your head out of the way by bending over to the inboard of the vehicle as you could with a stock street seatbelt. Again, if you are intent on racing, you need to get a copy of the current GCR and ensure that your bar meets the requirements for your intended class of competition.

Strength and Configuration Considerations

Roll bars come most commonly in four different configurations:
(1) wide (two seat) single hoop - no diagonal,
(2) wide (two seat) single hoop - one diagonal support,
(3) wide (two seat) single hoop - two additional rearward, and
(4) Driver's side hoop - one rearward or diagonal support.

The full roll cage is not addressed here only because I chose not to classify it as a "roll bar" for the purposes of this writing. Of the four listed above, the most common of these seen on the street are 1 2 and 3. If you look at the E Production race cars however you see the 4th category in common use. This last configuration is really beyond the scope of this writing, and we will concentrate on 1, 2 and 3.

The single hoop can either include two or four mounting points. The simplest types are attached only to the top of the seat belt towers and should be considered "style bars" since their integrity is severely limited due to the method of attachment. Some types however have an extended length for attachment both at the top of the seat belt towers as well as further down on the shell of the seat belt towers (and closer to the 'frame' of the vehicle). This latter configuration has been deemed by some racetracks and drivers' schools as a "four-point" attachment (which term classically identifies a much stronger configuration).

The purpose of the diagonal and the two rearward supports in configuration 2 and 3 is additional strength in the all directions. A hoop itself provides the necessary vertical strength, but is relatively weak in a fore-aft direction (consider the impact of a foot-long moment arm of the bar height acting on a two-inch attachment point around which the bar attempts to rotate in an accident). The diagonal or the two rearward support configuration provides this needed fore-aft strength and extends the attachment plane.

Materials used in most bars will be cold-rolled steel typically characteristic of 70,000 psi tensile strength. For approximations, materials engineers typically use about 1/4 of the tensile for anticipated shear strength, thus 17,500 psi. Assuming a 2.5 inch diameter tube with a 1/16th wall thickness (cross-sectional area = 0.5 sq inches), one tube of the bar will support a 35,000 pound vertical force but only a 8,750 pound force laterally. These loads sound extreme but if you consider the loads as you are decelerating from 100 mph to 0 mph in a matter of seconds (let's say 1 second for simpler calculation purposes) where a max load could be as high as 4.5 g, you've just applied over 10,000 pounds of force with your 2250 pound car!


Bars are either bolted or welded into the vehicle, although for the vast majority of bars of the 1st and 2nd type, the attachment is by nut and bolt. All Style bars as well as most roll bars are bolted in. I have heard (but not seen in writing) that there is a preference for bolted attachment to prevent structural integrity degradation (to the vehicle) from the welding process (specifically localized embrittlement). It also happens that the Miata doesn't have a lot of major structural members to weld to.

When selecting fasteners, realize that there are various grades of quality associated with nuts and bolts. If your roll bar is for safety purposes, don't skimp on cheap grade fasteners. The cost of nuts and bolts is not high and you can get a good grade 5 or 8 bolt for just a little more. I would recommend no less than a grade 5 fastener being used on a roll bar installation (grade 5 is indicated by three equally-spaced radial lines around the top of the bolt head). Generally, markings on the head of the bolts will indicate the grade of the fastener. Those quality criteria are not within the scope of this page, but there are many good references available to explain these characteristics to you.

Other Safety Considerations - Padding

Discussion on the net has included comparisons to the padding sold for roll bars to that available at your local hardware store for pipe insulation. They might look similar, but don't assume that they are. I don't know of any conclusive testing that has been done, but rumor has it that there is a BIG difference. For the small difference in price (on the order of single digit dollars), it isn't recommended that you skimp here. Use the right stuff.

There are probably a variety of padding attaching devices available as well. These aren't so critical as the padding itself, but they may include a characteristic of locking mechanism that represents a hazard. A common version of these is commercially identified as "Ty-Wrap" and made of a nylon-like material. They come in a variety of colors, but most often black, blue or translucent white. You will find these in your car's wiring harness already. When attaching these you will want to avoid orienting the locking end so that they are positioned behind your's or your passenger's head.


Hard Dog Sport Bar
The following is a brief exchange that ensued in 1994 about the Hard Dog Sport Bar (a type 2 bar as I have classified them above). This posting was liberated by Steve Ling.

Has anyone installed the new Hard Dog Sport Bar that appears in teh summer Miata Magazine?

1. Remove lots of parts around the seat belt towers.

2. Remove the rear carpet. A small claw hammer works great on those damn plastic tacks.

3. Remove a panel over the gas tank.

4. Spend several minutes trying to figure out how to read the pattern for cutting the sheet metal for the rear braces.

5. Spend several hours cutting the sheet metal. Send me email for some more details.

6. Struggle to get the bar in place. Call a friend to help. (Have him/her bring cold beer.) Eventually get the bar in place. Find out it must be removed to cut more sheet metal. (Give up for the night and drink the beer.)

[6.] If you have ABS, the wires to the rear sensors must be relocated. Email for details.

7. After the bar fits, install the bolts to the seat belt towers to hold it in place. Drill holes for the rest of the bolts. Have a strong friend handy for torquing the bolts to 50 ft-lbs.

8. Put the carpet into position. Realize that there is no way to cut the carpet for the bar until the carpet is in position, and no way to put the carpet in position until it is cut for the bar. Make a guess and start cutting.

9. Leave the trim off the seat belt towers until you've had time to rest. Cutting it accurately is important. Mine have been off for months.

As a side note, the driver loses no seat travel, and the passenger loses maybe an inch or two. I asked Craig at Hard Dog to make the cross brace removable. I run without it on the street so I don't have to look at it in the mirror. With the cross brace removed the passenger seat has full travel.

This may get me thrown off the list, but I leave the window zipped and just fold it with the top. There's no place to put the window if you unzip it. Just make sure it doesn't kink as it folds.

Could a neophyte install it? A determined one.

Thanks Steve for allowing us to republish this communication in the Garage. (Look for Steve's email address in the online directory if you really want to email him.)

Pylon Motorsports Sport Bar
Kate Hughes installed her Pylon Motorsports sport bar (a type 2, as I have classified them above) in 15 minutes (she swears) with no cutting or drilling (except in their bar). Her bar has a diagonal that enters the passenger area, but at the time of her posting in June 1994, no passenger had ever complained about it. That bar bolts to the seat belt towers and its third member bolts to teh passenger's seat track.

Hard Dog [?] Bar
Ken Walker in Houston installed a Hard Dog bar that used only two mounting points at the top of the seat belt towers (a type 1 bar as I have classified them above). His opinion included compliments to the Hard Dog company for their good instructions.

He indicated that the installer would need tin snips, a coarse file, a 1/2 inch socket wrench and assorted sockets, and an air conditioned garage.

His experince was similar to mine in that a downward pointing bolt is difficult to thread a lockwasher and nut onto up inside the top of the seatbelt towers. Ken used a dab of locktite to hold his washer in place while threading the nut on. [I taped the washer and nut together and threading them together onto the bolt, then pulled the tape off and torqued them down (up).]

Autpower Street Roll Bar
James Wynn installed an Autopower Street roll bar (a type 3 as I have classified them above). James was a little critical of Autopower's instructions, but concluded that "you can figure out what they are trying to say." He recommends having someone else do the installation and specifically noted the reiterative fitting and cutting the shelf that he had to do to get it correctly installed.

Racing Beat Style Bar I
Drake Daum installed a Racing Beat Style Bar I (a type 1 bar as classified them above) and it fit great with the softtop. Then when winter came, he attempted to install the hardtop and there were interference problems. He had to disassemble the bar and return it to the vendor for a new version (at that time - spring 94) that was designed to fit the hardtop-equipped vehicle.

Drake adds that the current bar that works with the hardtop does not impede rearward vision any more than the first bar. The kit provides spacers to allow the installer to lower the inside rearview mirror by about 1/2". This helps, but the lower edge of the horizontal portion of the bar is still in view in the mirror.

Bar attachment points were perfectly aligned, hardware was good, fit and finish were excellent, vinyl covered padding is really nice looking.

The written directions were good, but the template for cutting the interior plastic trim panels was very poor. Drake has developed a very precise template for cutting the trim panel around the bar's attachment point at the shoulder harness tower.

Removing the plastic cover around the mirror mount without destroying it is the hardest part of the whole installation!! The bar bolts on very easily. One must remove the door sill trim and plastic quarter panel trim around the seat belt shoulder harness tower. Also remove the outside lower belt anchor bolt. Once the trim panel is out, remove the shoulder belt inertial reel and merely set it down behind the seat.

Both Drake and Ken have since installed bars for other mebers in their respective clubs and welcome any email questions that they might be able to help with.

Getting the top up and down and Interference with the back window

Top clearance is a problem with some bars and requires careful installation to avoid interference with either the convertible top frame or the hardtop. When you are selecting your bar make sure you ask the vendor about hardtop and softtop clearances. Believe it or not there can be up to 1/4 inch difference between dimensions in Miatas. My Style Bar II had to have 1/4 inch removed from two points on its baseplate to clear the softtop frame (near the seat belt towers) while some owners report little or no interference problem at all.

A significant consideration in selecting a bar is its interference with the back window. Obvioulsy, if you need a specifically-configured bar to satisfy racing requirements, you don't have much choice, but keep in mind that if you do have some choice in the matter, many bars with diagonals and rear-ward supports will not allow you to lay your convertible top window down like it did when the car had no bar at all. In fact in some cases you won't even be able to reach the zipper easily. If you have one of the new glass rear windows, then you have even more restrictions to the bar type. At least one Miata owner that I know has the glass window and the Hard Dog Hard Bar. The Hard Bar has no diagonals the ability to grasp the top handle and single-handedly raise the top in one swift movement as you used to. Now you will be forced to get out of the car to put the top up, or have the passenger help you with it.


The two finishes that I have seen available with different kinds of bars are powder coated black and chromed finish. A few months ago I heard about a powder coated white finish, but have yet to see one in person. I would assume the latter finish could be painted to match the car's color, but again I have not seen any such treatment in person.

The chrome finish on some bars is not perfect. Look closely at the corners and the welds to ensure that there is good anodizing. A poor process is indicated by a variation in surface texture and/or discoloration.


Cost for the style bars and roll bars starts at about $200 and climbs on up depending on the complexity and integrity. For some reason finish does not seem to impact price in most cases.

Well I hope that this has shed some light on the vast topic of bars. There are lots of them out there and a lot of Miata owners that have them installed. Almost anyone with a bar will be glad to talk to you about it so don't hesitate to ask. In the meantime feel free to email me with questions or comments. I can't guarantee a quick answer, but I'll see what I can find out.


Email me at and thanks for responding!