Everything Frame Rail Brace Related

[Dehamsta]

I have installed mine a while ago now and the problem i have is that the nuts/bolt can be felt underneath my feet.
Not a big deal but it is something to be mindful of and you might find a way to fix it during the install while the seats and carpet are off.

thanks for the tip mate, i wonder if a piece of tape over them would lesson the feel through the carpet?.

Unfortunately, i don't think that will work. I was thinking you probably need to add a layer of firm insulation with cut outs for the nuts/bolts so the floor is more level with the tops of the nuts and bolts. Maybe dynamat or something similar.

[Alex 2550]

Unfortunately, i don't think that will work. I was thinking you probably need to add a layer of firm insulation with cut outs for the nuts/bolts so the floor is more level with the tops of the nuts and bolts. Maybe dynamat or something similar.

hmm interesting i may have something that will work that is lighter than the Dynamat, or maybe ill just live with it
thanks for the heads up mate, all these things help and is what i was hoping to achieve with this thread.

[Rolley]

I've been thinking about the bolt head situation too and am looking into getting a backing plate to go inside the car that matches up to the holes in the rails. I can then cut square holes in it and use dome headed stainless coach bolts.

[Gladiator]

Keep up the good work fellas. Hopefully by the time I get back from holidays, you guys will have solved all the problems & I can just go ahead & fit mine.


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[KevGoat]

Can't help feeling there's maybe some over thinking going on. Appreciate Dehamsta's feedback (and certainly something I'd thought about) but these rails have been fitted to MX-5/Miata's for years and I can't recall ever reading anything anywhere about the bolts/nuts being an issue.

That said, if I can even feel them slightly, my OCD will play havoc ...

[Aiming Faster]

The mechanic who assisted me fit mine was surprised how much the floor moved when tightening the bolts, supplied me a bunch of large OD washers to go on the inside for more support. The hard top made a more noticeable stiffness difference, still surprises me each time I drive without it on!

[Mr Morlock]

I dont think Rolley's solution is an easy one to execute. Cutting an accurate sq hole to accomodate the bolt ( like a coach bolt) is not easy. If the hole is not perfect then the sq shank integral to the head may turn in the mating part i.e. cam out.

[hks_kansei]

I'm with Morlock here, especially since the floor pan is thin pressed steel.
Plus, a square hole has the forces concentrated at the corners, which can encourage them to split there (hence why planes don't have square Windows and doors)

Ideally for the coach bolts you would weld a plate over the holes to strengthen it etc.
But if you're going through that much effort you may as well just weld the rail braces onto the car and skip bolts all together.

A better plan I feel would be to use round headed internal drive bolts, like Allen key ones or something.
You can then use a standard round hole, with the benefit of being able to tighten them still.


As far as roadworthy, in Victoria, if you go by the letter of the law, these won't pass since you've drilled/cut a structural part of the car (floor)
Same part of the rules that make cars fail for having speaker holes cut into the parcel shelf.

[Rolley]

You're Forgetting how long I farted round filing out my speaker covers, a couple of Square holes in some plate is not going to be any hassle at all!

I still think having the bolts, whatever kind you choose, supported either in a plate or larger diameter panel washer will spread the load across the floor sheet better than just the bolt heads and 20mm washers supplied on the inside of the car. I may be completely off the mark but for me it's just time, doing it definitely wont adversely affect the end result.

[LiteIsRite]

Just a quick post to say that I've tested the brace surface as a jacking point, now that I have a low profile floor jack (thanks to the wife for going to the local SCA today and grabbing the last one there for $73). Works great, as others have said, at a point directly in line with the door mirrors.

[LiteIsRite]

Took a proper drive this morning, over 180km of varied (sealed) road surfaces, with my usual co-driver in the passenger seat.

I'm pleased to report that my initial observations, made just after the braces were installed last Saturday, hold true. The improvements in NVH, while subtle, were clear to both of us. Some '65 mph shimmy' is mostly cleared up as well. I had thought after my initial drive that the steering was heavier (no PS in my car), but it must have simply been my post-installation tired arms

BTW, neither of us noticed the bolt heads through the carpet.

I look forward to reading your experiences.

[bruce]

You'd think underlay, carpet and floor mats would prevent you noticing any bolt heads.

[KevGoat]

Got motivated late this afternoon and got the car settled on stands, seats out and carpet up and had some time to do a trial fitment of the rails.

Driver's side all lines up nicely, but struck a small problem on the passenger side - maybe just an NB thing. The rail on that side has cut outs that look like they should line up with some dimples and seams under the floor, but if I line these up, one bolt would be inside the seat mount inside the car (similar to what happened on the MiataMods video). I drilled a small 1.5mm hole to check. I need to move the frame forward about 12mm, which actually sits it more like where it is supposed to be as per the instructions (and where MiataMods suggests) but is then sitting on top of those raised sections.

So I looked up heaps of photos of rails fitted and most don't even have these cutouts, they all seem to just sit on top of those raised parts, so I came to the conclusion it's not an issue and I'll just ignore the cutouts and sit the rail so I can get that bolt in properly.

[KevGoat]

Finished fitting mine in today. Takes a while with all the on/off, checking positioning etc etc. Bit scary once start drilling and definitely one of those check ... double check ... then check again jobs. My back and arms really know about it now

As has been mentioned before, good drill bits are essential. I had a number of bits in the sizes required, but once I started it became obvious they weren't as good quality as I thought and this caused me quite a bit of extra effort. I drilled pilot holes then removed the rails so as not to damage them when I drilled the full size holes - wrong! The tolerances are really tight and the holes need to be perfectly placed. Some of mine ended up slightly off center and I had to drill them out a bit more to fit the bolts through.

Very satisfying once all back together!

Took it out for a short drive. Can't say I noticed much difference with my SE with the hardtop still on. There was a feeling that the car handles bumps and irregularities a lot better, hard to explain. Sort of feels like the suspension is working better, hits the bump and that's it, solid. I 'd need a good drive down the coast or through the hills to get any further impressions and I'll be most interested in how it feels once the hardtop is off.

So, at this early stage, would I say it's worth it on later model NB's? ... On how it felt after just this short drive, I'd say yes

[LiteIsRite]

Finished fitting mine in today.
My back and arms really know about it now

Yes!

Which is why I mistakenly thought my steering was heavier on my initial drive

Well done, Kev. I imagine you'll feel more of a difference with the hardtop off?