Harness mount location & Sparco
 

Hope this belongs here.

I have modded the factory rails to accommodate an older set of Sparco seats I have. Just a re-drill. Not cardboard and dreams or anything. Easily as sturdy as the factory ones. However, I have a set of 4 points that came with the car and would like those in , as the factory 3 point doesn't set as well in the lap and I don't trust it. I plan new seats in the future and 5 points later, but not in the budget now.

I have the shoulder ones going tho a harness bar, the door side of the lap belt goes to a big eyelet bolted to the factory seat belt spot, but the trans tunnel side of the lap belt is causing concern.

To get the car driving I mounted them like this. (Tightened down thought)
https://www.miataturbo.net/attachmen...ine=1374267798


I don't feel as if it's the most optimum way of doing it. I pulls on the mount odd to me. Safe? The bolt is plenty long.

However, if I use the eyelets in the seat rail factory belt location the seats don't fit. Well they might, but it may take more violence than I want to give.
Attachment 239590

Do I

A- Mount it the way I had before the the rail bolt under and back and the sheer pull will be fine?

B- Sledge hammer the trans tunnel to let the eyelet have enough clearance to let the seat mount/slide?

C- Other options.


I am WAY more concerned with safety than a $20 part.

There is a mount point on the trans tunnel, just like on the B pillar. Could be behind the carpet.

Yup, there's a spot on the tunnel near the corner. Below the hole that the 94+ seatbelt receivers bolt to. Same thread, but probably behind some carpet. Had mine in the upper mounting hole before I discovered the other hole (:giggle:)

4-point harnesses are significantly more dangerous than factory 3-point belts. There have been a handful of deaths at HPDE events in California over the last 10 years, and at least half of them can be directly attributed to use of a 4-point seatbelt. They have been banned by almost every sanctioning body, including NASA and SCCA, and at least one popular HPDE group (Speedventures) explicitly bans 4-points from any car that runs at one of its events.

You are significantly safer wearing a factory 3-point belt in a stock seat than you are in a racing seat with an ill-fitting belt, or worse yet, a racing seat with a 4-point belt. If you can't afford to upgrade the entire safety system, then don't touch any of it.

Start at 0:10:


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wow... that's an epic 3 pt vs 4 pt vs 5/6 pt video. Stick a fork in this one.

Okay so the 4 points are getting yanked out today. Glad I didn't pay for them (PO). The factory belt sits on my lap pretty snug even in the Sparcos. It sits right across the belt line exactly where my other Miata's factory belt and the one in my Jeep sits. I'll need to get the of belt guide brackets for the roll bar. They don't like retracting now as it sits.

Anyone have issues with these?
https://www.miataturbo.net/attachmen...ine=1374343707

Link - Boss Frog seat belt guides - MiataRoadster - High-performance customer service...and parts for Roadsters


I only have the the factory passenger seat and belts for both sides minus the catch on the passenger side. The previous guy didn't have it all at the time. I'll source the catch soon. Or other seat options/opinions greatly welcome. Anything that will work with the factory belts.

Then, what should we use?

5pt SB or even 6pt? Is there a huge difference between the two?

And which are the correct bolting points for a Miata (with rollbar/harness)?

6 point. I've seen a 5 point do some very bad things in the event of a crash...

harness mount points should be based on the manufacturer's suggestion. Scroth has their manual on the website and it gives you angles and distances you need to figure it out.

With that said, the miata is a bit tricky as the frame rails are right under you and mounting to the floor with eye-lets means you may not be able to get the perfect placement for lap belts. For sure the shoulder harnesses should be easier as you can get a custom harness bar for the seat height.

5 and 6 point belts are safe in general. The 5-point belts are "frowned" upon because they could damage your family jewels. I find that V-Style 6 points don't help too much unless your camlock is very high up. The U-style (not sure what they are called, look at the scroth profi belts) ones do a better job, but they can be a bit more intrusive if you are a big guy.

Check out Schroth's Profi-style sub belts. They fold back on themselves so the subs actually ride against the inside of your thighs, vs. directly on your nutsack. I always had to make an undignified adjustment when I was using G-force 6-points (t-style), but with the Schroth subs there's never been a need.

I have the profis. I know what you are talking about. I am saying the V style belts can still do some damage if they are too low. The "t-style" as you call them, don't seem as prone to that.

All I meant by more intrusive is the metal bar that constitutes the "t". It seems like it could be all in your thighs if the seat isn't wide enough...

Off topic a bit but that video reminds me why I am very happy I bought a HANS over the winter.

Not all 4-points are bad. In fact some perform so well that racers mistake them for 5/6-points.

4-point ASM vs 6-point would be interesting to see.

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Reviving this, seeing the above video/arguments; how are non-ASM 4 points even FIA/SFI approved and sold as such? If they're such a far cry from being safe, why are the approved?