MX5Plus Twin Hoop Roll Bar install - NA6 - my experiences

[rpost77]

Nevyn72 has a thread relating his experiences installing an MX5Plus twin hoop bar into an NB.

It’s a useful thread and helped somewhat with my install into a 1990/1 NA6 (along with some others found).

I will add here my thoughts and tips on my install - the NA6 is slightly different with its own set of unique issues.

This is the first major mechanical/automotive maintenance I have done - I’m an IT guy and have never attempted anything close to this before - I’m reasonably pleased with the outcome and certainly learned a lot (and lost a bit of skin and a lot of sweat in the process!).

1) 2 people - you could really do it by yourself in a pinch but a 2nd pair of eyes and hands really helps. My partner (completely non-mechanical/technical) helped me out and endured my screaming and cursing and was a huge help.

2) Take out the seats. This is easy - four bolts each and you will be thankful for the extra room - particularly when doing the rear pad bolts as you can only do this with the soft top up.

3) Measure twice before drilling/cutting etc. - then before drilling/cutting measure again!

4) The NA6 does not have the threaded hole or the cutouts in the seatbelt trim for the bolt (I believe NA6s from about 1993 and NA8s had the cockpit brace so will have the threaded hole and cutout).

The roll bar comes with a captive nut plate for each side to provide a thread to attach the bolt to.

There is an elongated slot next to the seatbelt bolt thread that will need to be widened to allow the bolt through - this hole does not have enough material to tap a thread into so you have to widen it and insert the captive nut plate underneath up through the seat belt cavity.

I used a cylindrical carbide burr to widen the slot.

5) You have to somehow fix the captive nut plate below the slot - I initially used a Selleys repair glue that claimed it would work - fail - I clamped it in overnight (that was fun getting clamps into the cavity) and the instant I put downward pressure on it (trying the bolt) it failed and fell to the bottom. I went to Bunnings and bought some black Auto Sikaflex and used that - covered the plate, positioned it and this time used a long thin bolt upside down (so head of the bolt sitting against bottom of captive nut) with the spacers on top and washers on top of that then a nut and tightened up to hold it in place overnight - next morning removed bolt/clamp and looked ok.

I found, however, when the time came to bolt this down, the drivers side plate began to drop - luckily the sikaflex is 'stretchy' so it didn't drop completely down - I was able to get a slim screwdriver through the hole in the trim that the tonneau catch screws into to stop it falling further and spent 10 minutes getting the bolt to catch in the thread. Once started, due to the plate being square, I could bolt it up and it 'dragged' the plate back up as it was tightened down.

Had the plate dropped completely I would have had to dismantle everything to fix it (not a pleasant thought by that stage).

Lesson from this if I have to do again - more Siakflex perhaps (careful not to get any squeezed into the threads) and position a thin screwdriver through the tonneau catch first before attempting to thread the bolt so you can ‘catch’ the plate if it drops.

6) Before you attach the captive nut plates - position the spacers and the plates and line them up.

The position of the spacer holes and captive nut plate holes are not centred - you need to match them and test by bolting together and keep the orientation that you settle on.

The spacer was easy - there is a 'shorter' side (hole closer to one edge) and this edge needs to be facing the inside of the car on both sides (otherwise the spacer hole will not line up with the widened slot hole and the bolt won't go through). The captive nut plates then need to be positioned in the seat belt tower cavity to match the alignment of the spacer, slot and bolt.

I used a sharpie to label each side of the plate so when it came time to fix it in I knew which orientation was correct (I labelled each one D (drivers side) and P (passenger side) then R, F, I, O on the edges (Rear, Front, Inside, Outside).

7) When drilling the holes in the trim for the side bolts - I made a template with cardboard - I positioned this over the side of the seatbelt tower and from the inside with a small screwdriver poked holes in the cardboard through the existing 4 holes in the tower side. I them positioned the template over the trim and marked the hole to be drilled.

You can use the 1 template for both sides (just don't flip it over when applying to the opposite side you took the template from).

Initially I drilled a 5mm hole and then used a christmas tree drill to widen to about 12mm (worked really well and leaves a nice clean hole).

Same attachment can be used to drill the hole in the top of the trim for the vertical bolts (or alternatively you could source NA8 trims to replace the NA6 trims as they already have these holes).

8) The spacers needed trimming - I used a Dremel with a grinding wheel and took a little bit off at a time checking each time until correct.

9) The pads that bolt to the parcel shell do not sit flat - no matter how you jiggle or position the bar.

The very rear of the pads sat about 1-2 cm above the shelf and the inside front of the pads also sat a little high.

I started a thread asking for help on this and others replied that this was 'normal' and everything would pull into shape when bolted together (i.e. the sheet metal of the parcel shelf would deform to fit when the bolts were tightened). I contacted MX5Plus and checked with them - their response was exactly that - normal and just bolt it together - everything would 'adjust' to fit.

The bolts for the pads are 10mm - I marked the holes as best I could (considering the rear holes were floating above the shelf) and used a right-angle drill to drill the holes.

In my NA6 I only had to drill 6 holes as there is already 1 hole on each side in the correct position (rear inside of each pad). I centre punched each hole before drilling to stop the drill bit wandering.

I initially drilled a 5mm hole then used a 12mm bit to widen.

I hired a right-angled drill form Kennards for the day - there is no way you could drill the rear holes without one if the soft top is attached - if the soft top is not attached then a normal drill would do the job (and the whole process would actually be a lot easier).

I drilled 12mm holes (reduced shank 12mm drill in a 10mm chuck) to allow for the funky angles the bolts would need to be at to mate with the bottom plates due to the gap at the rear of the pads. I got the holes pretty accurate - even so, when the time came to install the pads/plates they proved to be inadequate.

10) Mounting the plates to the pads was an exercise in frustration. Due to the floating of the pads at the rear, those bolts were slightly angled and I had huge problems getting any of them started. I could get the front ones going but not the rear or vice versa.

I found removing the plate (held by 3 screws) in the parcel shelf in the passenger side helped with accessing the plates from inside (had help holding plates in position from partner) and made that side a bit easier. The passenger side is difficult to access from the boot due to the fuel lines - the drivers side is relatively easier.

In the end, I needed to break out the carbide burr and, with the roll bar pads in position, widen the drilled holes using the holes in the pad as a ‘guide’. I placed the burr in the pad holes and widened the parcel shelf holes in line with those.

Once that was done, getting the bolts started in the plate holes was easier (although still awkward). Once all were started then they were tightened progressively. The tightening was accompanied by creaking and popping sounds as the parcel shelf ‘conformed’ to its new shape. At the end, everything turned out flat and compressed. You need some stamina as each bolt seems to take a million turns of the ratchet before it’s tight - I can see the advantage of a pneumatic rachet gun here for sure!

11) I had partially bolted the top and side bolts at the from of the bar prior to installing the pad bolts and tightening them. Once the pads were done, I tightened the top and side bolts. I found the top bolts got to about 1 cm from complete then got really difficult to finish - more elbow grease and leaning on the ratchet got them done finally.

All in all an interesting exercise. Hope this info may be of use to someone with their install.

Ralph

[gslender]

Nice write up!

Sent from my GT-I9300 using Tapatalk

[Nevyn72]

Nice work Ralph!

These bars can be a bit tricky to install but well worth it when done.
The more people share their experiences, the easier it will be for others to do the same install down the track.....

Thanks for sharing.

[OurCognitiveSurplus]

I had exactly the same problem with the sikaflex. Ended up working some magic with a coathanger to make it work - but it was just the worst. There needs to be a better way.

[hks_kansei]

Don't the captive nut plates have a small hole in a corner to allow you to put a single rivet in and stop any rotation/movement?

I remember a set of rollbar instructions that mentioned that, I'm pretty sure it was MX5+? (I don't think Brown Davis had any captive nuts, only realy annoying spreader plates with separate nuts)

[rpost77]

Not the captive nut plates - the side bolt mounting plates have the small hole and rivet that you mention - installing that part worked no problems.

Now that you have triggered the idea - I think that next time if I have to do this, drilling a small hole(s) in the captive nut plates and the spacer and/or the seat belt tower next to the slot and riveting the plate to hold it (like the side bolt mounting plate) might be the way to go.

Don't the captive nut plates have a small hole in a corner to allow you to put a single rivet in and stop any rotation/movement?

I remember a set of rollbar instructions that mentioned that, I'm pretty sure it was MX5+? (I don't think Brown Davis had any captive nuts, only realy annoying spreader plates with separate nuts)

[CatchyD]

Thanks for the write up, just bought a MX5Plus Single Hoop Torque Box Roll Bar and shall be tackling the task of installing it with a mate this Thursday.

These tips and tricks shall make installation a tad bit easier!

[rpost77]

Update.

Finally got a seat back in and went for the 1st drive with the roll bar installed (while in the car I took the opportunity to do a bunch of other things (radio reseating etc.)).

First impressions - like a new car! A lot of the body shake previously noticeable is simply gone and the car feels "tighter". Drives and handles the same (did not expect any difference) but definitely notice considerably less 'scuttle' in the body when hitting bumps or uneven tarmac.

I notice more now the suspension, springs and wishbones doing their job rather than the body movement that tended to drown this out.

Tends to highlight the other rattles in the car now (door cards etc.) so they can be focused on and cleared up next.

Something I did miss - I didn't replace the 2 plugs/clip in the side trim before installing the bar - as a result the bar completely covers the tonneau catch hole (redundant anyway as the tonneau can't be used) and half covers the pop out plastic clip - can't squeeze the clip in beside the roll bar side plate to get it back in. I haven't noticed any rattles or squeaks due to the 2 missing bits but will try to come up with a solution (at least to the pop up clip as it is a bit obvious).

Lesson learnt - put these 2 bits back before installing bar (although to be honest - not sure if the tonneau clip would have fouled on the bar anyway).

Also, I put the lock bar and harness bolts in (have to do this before installing bar otherwise you won't get the locking plate in afterwards). I thought long about this - I don't plan on ever using a harness and considered just getting some plastic plugs for the hole but in the end I decided to install them in case I changed my mind.

I don't like the silver nuts of the harness bolts (or the other bolts) against the black of the bar so I ordered some black plastic nut covers from eBay which arrived today (10mm and 12mm). They cover the bolt heads and look OK - you can still see the rim of the washer underneath but definitely an improvement. If anyone can suggest a better solution I am all ears.

My car is 24 years old this year - I have owned for 22 of those - wondering why I didn't do this 10 years (or more) ago - makes a real difference (and looks great also - I have NB8B leather seats and they work well visually with the bar).

My advice to anyone with an NA is to go for it - you will appreciate the difference it makes.

Ralph