Introduction:
Firstly, if you plan to carry out any DIY work on your car PLEASE ensure that you use correct protective personal equipment (PPE), tools and circuit breakers for electrical equipment. As an absolute minimum, if you are planning to jack up your car, do not work underneath unless the car is correctly supported on axle stands. NEVER work underneath a car supported purely on a jack.
Secondly, this thread is designed to be an ‘eye-opener’ to all the jargon that surrounds the mystery of these items. In truth choosing your bar is far harder than actually fitting it!
Thirdly, the MX-5 very VERY rarely flips! Please do not read on then panic that the next time you go out for a drive you are going to find your forehead rubbing on tarmac! Many Club members have attended plenty of track events with no additional modifications to their cars without incident.
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So, you’ve done a Ma5da Racing parade lap, been out on track for the first time, or thinking that “just maybe I’d like a bit more roll-over protection?” Where do you start?
WHY FIT A ROLLBAR? short video containing a Ma5da Racing incident at Snetterton. The driver made a full recovery, his car did not.
Bars: ‘Style’ and ‘Roll’;
A style bar is purely that - a bit of bling, somewhere to secure your windblocker! - and whilst some are made of quite chunky metal they do not claim to provide any form of roll-over protection. The chances are, however substantial a style bar may look, the thickness of the metal tubing will not offer the required strength in the event of the car flipping. Any bar that connects across the seatbelt towers will add ‘bracing’ (in the same way as the later Mk1 1800 ‘brace-bar’ reduces scuttle shake) but this should not be confused with roll-over protection.
By design, a roll bar offers the necessary strength and rigidity to support the weight of the car if it turns over, whilst also being robust enough to withstand the dynamic forces a roll will induce.
Which one?;
Cusco, Il Motorsport, Hard-dog, Safety Devices, TR Lane and a hundred-and-one eBay ‘specials’ are available. Research what you require carefully, many bars are Japanese/US imports and are likely to suffer excessive carraige costs and import tax on top of the quoted price. UK based companies are limited but offer incredibly well made products and prices vary between models. The term ‘buyer beware’ is particularly apt when buying from auction sites; do you really want to find out that the bar that you got as a ‘bargain’ online actually doesn’t do what it said at the very time you need it to?! Personally I would always choose to buy new, or from someone within the Club who has bought the bar new and can confirm it’s history. For quality look for ‘TIG’ rather than ‘MIG’ welded products.
Main manufacturers:
US/UK/Australiasian brands; The main ones are:
TR LANE Fabrications: By far the largest selection of MX-5 safety components in the UK. TR Lane produce rollbars (the four main designs being the TD - track day, GP - General Purpose, TT - cobra look-a-like and the best mix of style and substance and the TDV - the track day bar but with twin diagonal bracing for maximum rigidity), harness bars (which also double as a brace bar as per the later 1800cc Mk 1), door brace bars and full roll cages. TR Lane also offer a bespoke service, custom building a bar to the requirements of the customer.
Hard Dog: US based company and seen by many as ‘the’ bar in it’s day. Still available (though finding a UK-based importer will prove difficult).
Brown-Davis: The steel version actually carried CAMS certification. It bolts to the seatbelt towers, but the rear stays sit on a large, thick plate that sits on the “parcel shelf”, and is securely bolted in place. There is also an aluminium non-certified version.
Safety Devices: Speedster bar. No longer in production, but sold by Moss for a long while. Black and chromed steel versions. Safety Devices did describe this as being designed using rollbar principles. The design was a twin hoop bar, braced via a frame onto the shelf. Safety Devices also make the full MSA approved cage for the Max 5 and Ma5da Racing series.
Caged: Responsible for the roll-cage for the Max5 race series, based in Frome.
Japanese brands; The main ones are:
Cusco/ Safety21: Same company. Cusco is the street branding, and the bars are usually aluminium, and should really be considered decorative items only. Safety21 is the trackday brand (not full motorsport), same bar designs, but in steel. In both cases, the bars could be had as 4P, 5P, 6P etc. Main bar bolts to the floor, usually tying into the seatbelt mounts, and bolt on stays into the trunk floor. Stays use redundancy in the design; if the bolt fails, the stays should jam onto the rollbar, and prevent total collapse. Like most other Japanese bars, these bars will result in a loss of seat travel. The brand is usually engraved into the bar at some place.
Carbing/Okuyama: Again, same company, different brands. Carbing is the street version, and some of their bars are also aluminium (polished finish). Again, a multitude of different configurations. However, these bars do sit quite far forward, and probably cause the greatest loss of seat travel. This does cause problems with a standard seat; most people will have to jam the seat up against the bar, to fit. The connecting bolt for the rear stays is very close to the skull. I managed to write off a brand new Shoei at Curboro’ with one of these. Usually identified via a sticker in the middle of the main bar.
D-Technique: Small backstreet tuning outfit. The bars are similar to the Safety21 bars, a little more “square” looking. No visible branding on the bar. 4P only.
Saito; Make road cages only. Quite an innovative design; the twin roof bars are curved towards the middle, allowing easy access to the cockpit.
“Rollbars” are not always required for sprints or hillclimbs; consult local competition rules. They are not specified for in the MSA Bluebook. Even then, I would suspect most scrutineers will pass a style bar. If the local rules do specify a “rollbar” for a road car, its unlikely they will go into detail on construction, measurements etc, as found for FIA bars. To my knowledge, only Safety Devices and OMP make a FIA compliant rollcage. Harddog bars are generally made to SCCA regulations; this is a technical standard that determines method of construction etc. It is not a test standard (Hard Dog bars have never been formally tested. The Boss Frog bar was “tested”, but not in a formal sense. In any case, because no blue book design specification exists for a road going car, a style bar will likely pass.
Attachment points; be careful here. The Autopower bar was the original rollbar that attached to the tops of the seatbelt towers, in the same way as a style bar, with rear stays reaching into the trunk. MonsterMiata produced knock-off of these; slightly lower profile. These were Chinese made, made by a company called RL Industries, who were best known for making a Chinese copy of a Soviet copy of a wartime German BMW motorcycle sidecar combination! If you are offered a chrome plated rollbar, alarm bells should sound; chromium electroplating may weaken the steel. On attachment points, there are some style bars (eg. Weapon R) which bolt to the seatbelt tower and the trunk floor. They are style bars though, albeit quite substantial. Ditto a Mazdaspeed “rollbar” (its not).
Bar versus cage;
A rollbar is generally secured into the car’s structure - often with attachment points behind the seats, into the rear wheel arches and onto the seatbelt tower bolts. Essentially utilising the car’s own strong-points. A rollbar will generally be a hoop located behind the seats across the width of the cabin with diagonal strengthening bars to provide both lateral and longditudinal support. A rollcage is a far more serious piece of engineering with the tubing extending forwards across the top of the doors and down into the footwell, essentially coocooning the cockpit in braced protection. Bar versus cage will always be tempered by price, need and access (anyone that has ever tried to clamber into an MX-5 fitted with a full cage and door bars will attest to the need for supple limbs!!!) Needless to say, unless you plan to participate in serious trackdays and or continue into competition, (or fancy parting with considerable money) a rollbar is the best balance of cost versus protection.
Any bone fide roll bar must have an inspection hole; generally on the driver’s side, in the main bar, and marked by yellow or white sticker/paint. This allows scrutineers, if they wish, to check the thickness of the tubing used.
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Thanks to ‘AT’ for his input into this guide.