I bought a second hand cabin brace bar for my Mk1, which seems a pretty substantial bit of metal.
However I was a bit concerned to find that you probably need to drill holes and it looks a fiddly job to fit one, as there are not any pre-existing points on a Mk1
What are the opinions on this - will it stiffen up the body as much as the cabin brace? How easy are these to fit? I am handy with a spanner, so not afraid of a bit of mechanical work.
You don’t have to drill any holes to fit the standard cabin brace to a mk1, the holes are there in the seatbelt towers. The only thing you will need to do is get some suitable washers and nuts/bolts as the holes in the seatbelt towers aren’t threaded on early mk1’s. Mine weren’t anyway!
That and you’ll need to cut the surrounding plastic to suit
Plus, whilst your link doesn’t seem to work for me, I don’t think mx5parts sell any actual roll bars…just style bars that look pretty but don’t serve much purpose.
I bought one for my wife’s Eunos and fitted it about 2 months ago.
The holes are there, some Mk1’s have a captive nut welded into the seatbelt tower in an existing hole behind the seatbelt top mounting bolt, in this case you can attach the brace and screw straight into it.
If not you will need some bolts (I used M12) and fitted the bolt up through the underside of the tower and through the cabin brace, with a washer and nut at the top.Trim the bolt to length to fit the finishing caps.
A certain degree of stripping down the interior is needed, and drilling and trimming of the plastic trim that shrouds the seatbelt tower.
I searched online and found a japanese translation of the method and some templates for cutting the trim to fit, the link may be on this forum somewhere.
It is likely to take you 3+ hours, to include the stripdown and refit.
Be prepared to take out the inertia seatbelt reel mechanism so that you can get your hand in the box section below the seatbelt tower, so that you can feed the bolt into place. (Eunos also has an electrical connection with wire (seatbelt tension relaxer fitted on this model).
In my opinion it braces the cabin as described reducing shake, but was introduced for the American market in relation to side impact protection concerns.
If you have the Mk2 or 2.5 windblocker as we do, then you will have to reposition the fixings. I simply reversed the metal brackets on ours and refitted it (losing access to the netting storage area (now behind the brace). But retaining the fold down capability.
As stated, if your car is a 90hp UK 1.6, the captive nuts are already present. All you need to do is drill a hole in the plastic trim. If there is no captive nut present (ie. any 89-93 1.6), then you have the conundrum of fitting the brace bar in place, before refitting the trim. So you will have to trim the plastic part differently from how Mazda intended, and how neat it will look will depend on your plastic carving skills.
Its worth the effort to fit the bar with the nut inside the seatbelt tower; I’ve done it both ways. The trick is to use a deep socket, with a dab of grease on it. The benefit is that the end piece trim will fit better. Another issue to contend with is that on the 1.8, there are different spacers on the seatbelt compared to the 1.6. So fitting the brace bar to a 1.6, without addressing this, the seatbelt reel trim will foul on the brace bar trim; tim the seatbelt rell trim a bit.
Personally, I found this to be of marginal benefit to the car. A quality style bar, from Racing Beat etc, will fit to each seatbelt tower via at least 2 mounting points, not just one. Plus, under all that rubber, the factory bar is just a 5mm thick bit of 1" flat steel.
Neither compares to the benefits of a properly mounted 4P or 6P rollbar.
A big thankyou for the comprehensive replies here.
It looks like a rollover bar is a better bet for me - easier to fit without damaging the trim, probably gives more bracing to the chassis and I get some rollover protection.
I doubt that. What needs to be done depends on the rollbar.
Most Japanese rollbars will have the main hoop fixed to the floor behind the seats, via 3-4 bolts, per side (need to be drilled through the floorpan). The rear stays then go through holes cut in the shelf, and bolt to the chassis. US Hard-Dog bars have the main bar fixed just in front of the seatbelt. The TR Lane bars, some of which appear to be clones of the HardDog bars, are similar.
Unless you mean stylebars, which will give no rollover protection. Have a search, and you will find references to the “mouse trap” effect, where a style bar, because its not braced, folds forward on top of the occupants in a roll, seriously injuring them.
Once thought to be theoretical, will never happen…
Buy it because you think it looks good, buy it because you think it will stiffen the car (but be careful; some will do a bettersome job than others), but don’t buy it because you think it might save your life. And some stylebars will require cutting of the trim.
My issue with those IL Motorsport bars are that they consist of too many parts; the bars screws to end brackets, that then bolt to the seatbelt tower, rather that being welded like Racing Beat. On the other hand, it is cheap.
My issue with them is that they aren’t roll bars. They may be more sturdy than a cheaper style bar but as they’re only fixed at two points if the unthinkable happened your car would look just like the one in the photo.
If you want protection get a proper roll bar. They’re not that much more expensive I paid £180 for my TRLane roll bar which bolts to the floor of the car at 4 points so is nice and solid. It’s also stiffened the car up far more than any brace bar could.
IMO, if you want to brace the chassis, buy a brace. If you want roll protection don’t make any compromises, get a proper roll bar to MSA spec tubing and at least four points with a diagonal. I’d only fit a weld-in cage personally but the shear loads on quality M16’s are greater than the tin you bolt it to.
I’ve been in a few rolls and take my survival space seriously
There’s a fair amount of well founded debate on miataforum about the safety implications of a rollbar installed in a car like the MX5. You are far more likely to be shunted or t-boned in a MX5, on the road, that rollover (the NHTSA statistics seem to bear this out), so does an unpadded rollbar provide protection, or become a hazard as your head flies about. And if you pad the rollbar, what with? Not pipe lagging I hope. SFI padding; without a helmet on, this stuff is going to hurt. So the expensive dual density padding?
A rollbar installed into a road car does not necessarily make that car more safe. Nor is a MX5 without a rollbar inherantly unsafe. A rollbar in a roadcar might reduce some risks, but introduces new ones.
And MSA tubing specs are meaningless. Read the blue book.
I think it should be considered that anything other than a well designed and fitted roll-cage is going to do nothing for your safety. It might increase risks in some types of accident and reduce them in others like AT says, but shuffling risks around is like trying to dodge raindrops…you are as likely to dodge into another as your are to miss the first and sod’s law the way it is, it’s not worth trying to work out which it will be.
All that said, EURO NCAP tested an airbagged mk2 and gave it 4 out of 5 stars, for the the most common types of smash, which is jaw-droppingly good for a car of this type so there’s not much need for improvement in the first place unless you’re doing motorsport or are very reckless on the road. However, EURO NCAP don’t test for rollover (mainly because there are so many ways to rollover, with varying levels of damage).
