Adding a 4 or 6 point harness to a Roadster - possible?

[3002 tii]

Originally Posted by eggman51

Much more clear - excellent reply - thanks. Apologies if my written form tones as dickhead, your thoughtful response is much appreciated. Keep us posted on how you go, I will make an effort to do same.

Cheers,
Eamonn

Not at all, if anything I was worried I was coming off as know-it-all but I wanted to be very clear on my points since we’re talking safety and I don’t want to spread misinformation.

Re the Corbeau seats, as important as fitment is I honestly don’t know much about their safety standards. But another option is the Cobra Nogaro, which is a name that’s more common in the track community (good review here). If money were no object I’d go for Recaro Sportsters but not worth the price considering lack of weight savings imo.

Originally Posted by Vanne

...
Eamonn, if needed mate, I can send you pics of how I went about it, I'll need to dig em up or take some new ones. Car is under 3 tarps ATM, hiding from the heat/sunlight.

If you can send me pics of the eye bolts welded to bulkhead, that would be great.

[eggman51]

Coming across as very helpful, tyvm.

Those Negaro seats are stunning!

I went for a Sparco QRT Performance seat because I think they will look OK along side the M passenger seat (can't justify 2 seats atm), they can accommodate a 6 point harness, but still look like a street seat, they are a decent price, narrow enough to fit in our cars, but still comfy for an aging fat guy, they don't have lots of flashy branding, and uh... I always wanted a Sparco seat



I also bought a Schroth Flexi 2x2 and the Schroth SHR Flex HANS device.

I am hoping to get that all installed and run on the track by the end of July.

BTW where did you find that pic of the harness mounted into the bulkhead (the one with the read seats) ?

Cheers,
Eamonn

[3002 tii]

Originally Posted by eggman51

Coming across as very helpful, tyvm.

Those Negaro seats are stunning!

I went for a Sparco QRT Performance seat because I think they will look OK along side the M passenger seat (can't justify 2 seats atm), they can accommodate a 6 point harness, but still look like a street seat, they are a decent price, narrow enough to fit in our cars, but still comfy for an aging fat guy, they don't have lots of flashy branding, and uh... I always wanted a Sparco seat

I also bought a Schroth Flexi 2x2 and the Schroth SHR Flex HANS device.

I am hoping to get that all installed and run on the track by the end of July.

BTW where did you find that pic of the harness mounted into the bulkhead (the one with the read seats) ?

Cheers,
Eamonn

Nice but are you ditching the 3 points? If not have u thought about how you’ll get around the lap belt issue?

Pulled from Facebook, some shop in west coast but saved down my personal folder knowing it’d be good reference later on. If I had to guess I think it was Cantrell Motorsports but not entirely sure. But they didn’t post many other photos besides that (hence why I’m hoping Vanne can send us something).

[eggman51]

Planning to keep the 3 points, might be into some territory I don't understand (yet again hehe).

Good find on that mount example, I could only find Vanne's and I googled a lot for such a config.

Cheers,
Eamonn

[3002 tii]

Originally Posted by eggman51

Planning to keep the 3 points, might be into some territory I don't understand (yet again hehe).

Good find on that mount example, I could only find Vanne's and I googled a lot for such a config.

Cheers,
Eamonn

Read the review of the Nogaro seat, explains the issue really clearly.

[eggman51]

Read it now in more detail, understood, will see what I can figure out with the Sparco seat. Thanks for pointing it out.

[jns_e85]

Subbed. +1 for more detail on that roll bar!

[kyriian]

^Following for updates on the rollbar

[sipman]

Not sure if this was mentioned earlier, but I think the 'old autocross trick' is the one where you adjust your seat to your track driving position, then set the memory as 2.
Slide your seat back as far as it'll go and recline it as far as possible. Buckle your belt in, pull the belt as tight as it'll go around your lap and feed the end into the B pillar while leaning back as far as possible. Now exhale and pull it even tighter, and quickly jerk the belt forward so it locks. Keep pressure on the belt and hold #2 on your preset and the seat will move forward to your original position and will keep tension on your belt when you let go.
Again, you'll feel squeezed out in paddock, but once on track it'll be fine.

This trick works will with the CG lock because the CG lock only locks your butt into the seat, not your chest. I was doing these together, and I eventually got tired of the belt buckle getting caught in my door sill because I left the CG lock attached. Eventually I realized I don't need to bother with the GC lock at all.

One other bit you may find useful. I posted about this previously but if you buy a replacement brake arm from your dealer (approx $20-30), you can cut the pedal pad off it and grind the weld off the backside. Clamp it to your existing brake pedal and drill 4 holes in the corners. Then use 4 flat head bolts and nuts and a series of washers to act as spacers. Put your rubber pedal pad onto the new metal portion now. You can then get your brake pedal closer to you, which will bring it even with your gas pedal when heel/toe downshifting.

Originally Posted by kyriian

Plenty of track groups would permit running a convertible without a rollbar, basically, once you sign the wavier you really are on your own.

For running my Z4MR on the track, I am leaving everything stock, and just use like CG locks or the old autocross trick to lock myself in place. Stock works and is tested, either you have a custom rollbar made, mount a proper 5-6 point harness and a proper FIA race seat in the car, or leave it stock. Personally safety is a do none or do them all sorta deal.

DS2500 is a dual purpose pad, a good dual purpose pad, but still not a proper track pads. Just remember, the more capable the brake pads are, the faster the pad eat rotors, and the more corrosive and dusty brake dust comes out.

[3002 tii]

Originally Posted by jns_e85

Subbed. +1 for more detail on that roll bar!

Originally Posted by kyriian

^Following for updates on the rollbar

After exchanging few emails with HMS, they're less worried about the factory roll hoops and more worried as to whether the bulkhead is strong enough to act as a mounting point for the shoulder harness. As per HMS, "Each individual shoulder belt can exert over 1500lbs of load on each individual eyebolt, and so the points these are anchored to need to be extremely strong, and I just don't have the confidence that these anchor points can provide that."

That assessment was not based on them having a Z4 to inspect in person but based on photos I had forwarded them. I know Vanne along with others went this route so maybe they could provide more insight but at the moment doesn't seem like I'll be pursuing this option. Ideally I wanted to do something like owner on their s2k sans the aftermarket roll bar (make sure to read down to post 15).

Btw uploaded old photos from my half cage install here.

[Vanne]

Not sure how that would be unsafe, though it's of course possible, as the original seatbelts are also mounted to the bulkhead? And there the impact weight is only distributed through one point, whereas with my setup the load is distributed through 2 points. I agree it's less than optimal, and a proper full cage is being looked at atm, but if your leaving your interior intact, not many other options. I am also not sold on the bulkhead being weak, as the factory roll hoops are attached to it.

I think Ian also had some pics of the way he did it, same as mine, might be easier to chase those up as mine is hybernating under 3 huge tarps/covers atm.

I also have to add, if you think it's unsafe, please don't do it. Mine is a little different anyways as where my roll bar is attached into the bulkhead, it's also welded to the chassis. On the subject of rollbars, not sure why everyone is attaching the bars using the rear shock mounts as an anchor point. Pretty unsafe too, but my bar builder says that if you do have a roll over, the wheels are 90% where the car will impact, which will directly force/distort the cage/bar probably nicely into the back of your chair. (Read, into you)

Ti, yours being an exception, as I think your other rollbar on your coupe was one of the only ones I've seen not tied into the shock mount.

I guess there are pro's and cons to everything.

[eggman51]

I tried the CG Lock this weekend. A definite improvement over standard 3 point. A bloody clever little bit of engineering! However it's no match for a full 6 point harness.

I am going to go ahead with a bulkhead mounted shoulder strap setup. I'm using the Schroth FIA approved backing plates from HMS.

I also agree with Vanne that the bulkhead is where BMW chose to mount the roll over hoops and the seat belt mounts. In the area of "liability avoidance" I suspect they did a fair amount of testing on the strength of the bulkhead.

I also agree with Vanne this is a personal choice and, given it likely would not pass tech at an SCCA like event without considerable expense spent on testing, each person needs to decide if they are OK with it and that the groups they lap with are OK with it.

I am *hoping* I can get my seat and harness installed by the end of the month, but I need to make time for it - lots of summer family stuff on the go.

[3002 tii]

Originally Posted by Vanne

Not sure how that would be unsafe, though it's of course possible, as the original seatbelts are also mounted to the bulkhead? And there the impact weight is only distributed through one point, whereas with my setup the load is distributed through 2 points. I agree it's less than optimal, and a proper full cage is being looked at atm, but if your leaving your interior intact, not many other options. I am also not sold on the bulkhead being weak, as the factory roll hoops are attached to it.

...

I guess there are pro's and cons to everything.

I actually agree with you and if I had to guess, their hesitation isn’t around the bulkhead per se, rather how the anchor points are attached to it. The bulkhead is probably fine structurally but unlike bolting to the floor, it probably requires way more reinforcement since there’s more lateral force being exerted than their is upwards from the floor. As long as the person doing the install is experienced and knows their stuff I would think it’s fine.

Only thing that sucks for me is there’s so much more trim removal involved with the roadster (i.e. soft top) in order to access the bulkhead.

Originally Posted by eggman51

I tried the CG Lock this weekend. A definite improvement over standard 3 point. A bloody clever little bit of engineering! However it's no match for a full 6 point harness.

I’ve read mixed things about CG, mainly the build quality. If you do a google search it’s not uncommon to reports of the plastic housing breaking. Not having one in my hand can’t tell if this is a trivial thing or a potential safety hazard.

[F360C]

Originally Posted by Vanne

Ti, yours being an exception, as I think your other rollbar on your coupe was one of the only ones I've seen not tied into the shock mount.

In additon to Ti's old setup the Weichers roll bar doesnt use the shock towers either. I was able to install it and get all the interior back in except the two small panels that cover the top inside of the rear quarter windows. I can easily cut them for install but have been lazy to do it because you can barely see their missing unless you really look.

That said I dont think the Weichers bar would pass inspection for any racing organization. It more a harness bar that adds some roll over protection.

[Michael9218]

Not sure I agree with the notion that if the factory belts use the bulkhead than it should be good enough for aftermarket shoulder belts. The factory 3 point mounts at the outboard extreme of the bulkhead and the bulkhead is strengthened and braced in triangulation for a forward load. Inboard shoulder mounts will not benefit from this structural reinforcement. In fact, towards the center of the bulkhead you can see it is more flimsy. Use of spot welds in the center section. As I recall from removing this bitch, the outboard reinforced area had some stitch welds. Much stronger.

Also, roll hoops are designed for a different load path. Pushing down, not bracing a forward load.

Hopefully this picture helps illustrate:

[3002 tii]

Originally Posted by Michael9218

Not sure I agree with the notion that if the factory belts use the bulkhead than it should be good enough for aftermarket shoulder belts. The factory 3 point mounts at the outboard extreme of the bulkhead and the bulkhead is strengthened and braced in triangulation for a forward load. Inboard shoulder mounts will not benefit from this structural reinforcement. In fact, towards the center of the bulkhead you can see it is more flimsy. Use of spot welds in the center section. As I recall from removing this bitch, the outboard reinforced area had some stitch welds. Much stronger.

Also, roll hoops are designed for a different load path. Pushing down, not bracing a forward load.

Hopefully this picture helps illustrate:

Michael - saw your build thread, quite impressive. You probably know this chassis better than anyone else on the boards. In your opinion, do you think there's any suitable location on the bulkhead (or a way to reinforce it) so that it can serve as a proper anchor point via eye bolt (plus threaded insert and plate)..

I know my roadster won't ever see w2w action but I really miss the ability to use my HANS for DE/TT. With bucket seats the factory roll hoops would provide more than enough clearance (i.e. more concerned about frontal impact and in the unlikely chance that a rollover occurs in DE/TT, I believe the factory hoops will do their job). So if I could run a proper "ASM" 4 point harness by anchoring to the bulkhead, that would be ideal for me. However, I recognize the irony of going through this effort just to compromise on safety. And last thing I want is to experience what this dude went through.

[Michael9218]

I suppose one could attach a harness bar that spanned across the front of the bulkhead. Clearance to the seat may be an issue, but at least the bar would attach to a structural location.

Not knowing the details, in that video it looks to me that the shoulder harnesses slipped out of the 3 bar slide wrap piece. Sadly, a fairly common mistake when not installed correctly.

Scroth instructions:
https://www.schrothracing.com/docs/3-bar-slide-wrap.pdf

[eggman51]

I looked into the detail of that video.. he bought a counterfeit $40 harness from AliExpress and the mounting clips failed. I think it was Darwin who first expressed "caveat emptor".

[3002 tii]

Originally Posted by Michael9218

I suppose one could attach a harness bar that spanned across the front of the bulkhead. Clearance to the seat may be an issue, but at least the bar would attach to a structural location.

Not knowing the details, in that video it looks to me that the shoulder harnesses slipped out of the 3 bar slide wrap piece. Sadly, a fairly common mistake when not installed correctly.

Scroth instructions:
https://www.schrothracing.com/docs/3-bar-slide-wrap.pdf

Re harness bar, I was hoping for something that would not require cutting into the factory trim, hence using eye bolts with inserts & plates on the bulkhead.

Originally Posted by eggman51

I looked into the detail of that video.. he bought a counterfeit $40 harness from AliExpress and the mounting clips failed. I think it was Darwin who first expressed "caveat emptor".

Correct, fake belts and the clips just broke right off.

[ANILE8]

For reference, can someone provide clear photos of how they attached the eyelets to the bulkhead?

Interested to know how this was done.

[Vanne]

Mine were (at the time) drilled through both parts of the bulk head and had a huge steel re-enforced mount behind the bulkhead. Is it safe? Nfi. I never tested it in anger (thank the gods) Felt solid though. Photos of said install sadly lacking though I've seen some from Ian's build.