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Schroth 6-pt harness questions

Old 11-13-06, 10:47 PM
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Schroth 6-pt harness questions

Hello,

I've got a '94 R2 with an M2 street roll bar. The harness attach points are on the replacement strut tower brace. I'm also using an HANS device. I'd like to get a Schroth harness for the car. My question:

1) Do I need to order a special belt length to make sure the shoulder harnesses make it all the way back to the strut tower brace?
2) I'm going to attach the lap belts to eye hooks that will replace the rearward seat rail bolts. Are these standard or do I need some special part for the FD?
3) I'm opting for a 6-point belt as I am using the stock seats and don't want to cut them up for a single anti-sub. I'm assuming that I can connect the anti-subs to the same eye hooks as the lap belts?

Or--is there a better installation than the one I've suggested? This is primarily a street car but will be driven with R-compound tires and over 500HP.

Thanks,

-ch
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Old 11-13-06, 10:50 PM
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Also: anyone that can recommend which HANS-compatible Schroth harness would be best for my application, I'd appreciate it. I'm leaning towards the Hybrid II-6H or Hybrid III-6H.

http://www.on-trackperformance.com/s...ness_index.htm

-ch
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Old 11-13-06, 10:52 PM
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Actually...maybe I need the Profi II-6H? That one has the buckle attached to the anti-sub straps. The Hybrid has the lap and anti-sub already attached which would make putting the harness on very interesting...

-ch
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Old 11-14-06, 12:27 AM
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If your using stock seats I wouldn't use anything more than a 4 point, the routing of the sub belt would be such that it would not restrain in the proper way....it would either be so long that it would be pointless or it could pull in such a way as to cause injury.
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Old 11-14-06, 03:14 AM
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Really? I thought using a 4-pt was considered dangerous by today's standards...

And I thought the accepted way to do the 6-pt with an OEM seat is to sit on the sub straps so that they go down between your legs, under towards the outside, and then back to where the lap belts attach. In this way as you move forward the anti-subs keep the camlock in place.

Is this wrong?

-ch
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Old 11-14-06, 09:41 AM
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That's the way most people do it w/ stock seats. I have heard that having the sub straps that way could cut off or sever arteries in your legs, but who knows, you can't allow for everything.

I will say that I found it horrifically uncomfortable. You get 'em cinched down and and you've crushed your nuts. I got a Sparco seat, but for the passenger stock seat, I was looking to just cut a proper sub strap hole and use a 5-point and a grommet of some sort...


Originally Posted by hyperion
Really? I thought using a 4-pt was considered dangerous by today's standards...

And I thought the accepted way to do the 6-pt with an OEM seat is to sit on the sub straps so that they go down between your legs, under towards the outside, and then back to where the lap belts attach. In this way as you move forward the anti-subs keep the camlock in place.

Is this wrong?

-ch
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Old 11-14-06, 10:50 AM
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I remember a Damien post a while ago about modifying the stock seats to have anti-sub straps but I wasn't convinced that this could be done without making things look awful. But maybe I'm wrong? Has anyone found some kind of kit that's designed to modify a stock seat for an anti-sub hole?

-ch
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Old 11-14-06, 12:57 PM
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the biggest problem with running an oem seat is all the extra padding under ones ****. in a heavy impact the majority of this padding will compress allowing for extra movement of ones body assentially equalling the same affects as loose belt's if you rout the sub belt over the lower side boulster its going to end up very long and in no way a straight line from the attach points thusly when they are asked to do there job they will compress all of the foam before they will try to restain you, assentially by the time they stop you from submarining you are already in a bad position and therefore could actually cause a very bad compression of your spine .

obviously your are concerned with your safety being that you noted that you would be running a hans "thumbs up" I guess I am a little curious why you wouldn't just complete picture and buy a proper racing seat?
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Old 11-14-06, 01:05 PM
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Sereneseven: I wanted to keep the car stock, and I already have an R2 so it would be a shame to dump those seats. I may do it eventually, but not yet.

I spoke with Schroth this morning. They said the following:

1) If you are using OEM seats (or aftermarket seats without a provision for anti-sub) you should ONLY use a 4-point harness. Do not modify the seat as it will compromise the structural integrity of the seat. They recommend their ASM (anti-sub) 4-point that has webbing in the shoulder harnesses that give during an impact, allowing your upper body to rotate slightly and reduce the submarine effect.

2) The only time you can sit on the anti-sub belts in a 6-point is in a formula car when the angle of the seat is 30 degrees or more.

3) HANS devices are designed with 5 and 6-point harnesses in mind. You can still use it with a 4-point but it is not nearly as effective.

4) They recommend attaching the belts to the factory belt locations where possible.

So I will go with a standard 4-point Schroth and probably use the HANS device anyway. When/if I get a racing seat I'll upgrade to a HANS-specific 6-point.

-ch
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Old 11-14-06, 01:08 PM
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I thought about giving these a try to "finish" the sub strap hole.

http://www.hmsmotorsport.com/store/s...c/seat-grommet
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Old 11-14-06, 01:13 PM
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That's a great link. I have to say that the Schroth guy put a bit of fear into me about doing this. He said that a lot of the structural integrity of OEM seats is the underside which is a stressed fabric. By cutting a hole there you weaken the seat. I'm not sure if this is true of all OEM seats, or specifically our FD seats. I thikn I'll pull one of the seats out this weekend and take a look. If there were a way to put an anti-sub strap there it would be pretty slick.

Has anyone that you know done this with an FD?

-ch
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Old 11-14-06, 01:16 PM
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The bottom of the FD seat is fiberglass... I rather doubt this would have any affect whatsoever on it's structural integrity.... I don't even see how it's a particularly stressed area of the seat.
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Old 11-14-06, 01:42 PM
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^well in normal use its not but in a high impact crash you bet it is, I've seen a lot of those cheezy plastic inserts in club cars and it scars me to think what happens to them if they are ever put the test.

bottom line if your going to go with a full 6 point harness get a proper seat

if your going to build a multi purpose car and you want to keep oem seats great, just get a 4 point but make sure that what your attaching to is strong enough.
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Old 11-14-06, 03:13 PM
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Yeah, it seems a shame to pull those lovely R2 seats, especially as it's a street car.

I think the issue is that racing seats are designed to handle transverse loads against the holes in the seat upon impact. (The anti-sub belt will be pushed forward and will eventually hit the edge of the hole.) If the seat isn't designed for it you could break the bottom of the seat. If that cracked I'm not sure what would happen to the other mounting points. I'll take a look this weekend...

Do you think you'd need one or two holes to do a 6pt harness in a stock seat?

-ch
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Old 11-14-06, 03:23 PM
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I can't figure out why you'd use a 6 point if you've got a sub strap hole. They're uncomfortable as hell. All the sub strap is there for is to keep the lap belt located on your hips properly.

I also can't see how the sub strap would ever damage the seat if it's installed correctly. The belt isn't going much of anyplace so long as it's attached to the other four straps.
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Old 11-14-06, 03:35 PM
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I strongly advise you not to try a six point with a stock seat it will not function in the manner it is supose to, with a six point it will ltranfer the the inertia of your mass down into the bottom of the seat which is not designed to handle this plus the seat bottom is not angled back enough to so it will force you into the sub belt at a lesser angle which can do all sorts of bad stuff to you. I gues what i am trying to say is that it will be no more affective than a standard 4 point so why butcher up your seats??

as for how many holes, in a properly positioned seat the sub should come through a single oval shaped hole.
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Old 11-14-06, 04:32 PM
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I had thought that 6-pt was the new 5-pt...I have a hard time even finding 5-pt harnesses from the top manufacturers like Schroth.

-ch
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Old 11-14-06, 04:35 PM
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I'm not sure what your asking. true most manufactures have moved to a 6 point .
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Old 11-14-06, 04:37 PM
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Ah, sereneseven, I get what you're saying. Instead of sub-ing, you go down into the seat--which is compliant and will let the lap belts/cam ride up high on my chest. Bad.

-ch
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Old 11-14-06, 05:57 PM
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I wouldn't use 4 points. When you tighten the shoulder belts it pulls up on the lap belts, moving them out of the safe zone (this happens in an impact too). The sub strap isn't really there to prevent submarining, that's not a problem on upright seats, it's there to keep the lap belt down.

My dad modified his Miata seats to accept 5 point harnesses. He cut an oval hole in the metal seat pan, lined the edge with some rubber hose, and slit the seat cushion and fabric, then sewed a sleeve into it and secured it to the bottom of the seat. The sub strap sits in the seat when not in use and isn't noticable by feel or by sight. It works very well and looks normal form anything beyond a few feet, and when close you have to look for it to notice.

Modify the seats, it'll be a better solution in the end. You don't want the shoulder straps pulling the lap belts up and causing them to push on your gut in an impact now do you?
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Old 11-14-06, 06:06 PM
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Do you have a picture of the modified Miata seats you're talking about?

There are so many opinions about this, and all of them seem reasonable. Very confusing.

-ch
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Old 11-14-06, 06:07 PM
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^ i thought i had explained this

now matter what you do your body will move down in an oem seat and theres a good chace that the seat bottom will buckle in a heavy enough impact with a sub belt thusly freeing up all kind of slach in the sub belt completly negating its usefullness so you might aswell run a 4 point with oem seat.
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Old 11-14-06, 07:30 PM
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I don't have any pics of the seat. You can also cut some of the foam out of the bottom of the seat to remove some of the compliance in the bottom of the seat. It can also help with keeping you in place by getting you deeper in the seat, increasing the boulstering. It'll also improve headroom and make the seat more comfortable. This is common in the Miata world, have a look around for "foamecotomy".

I've tried the 5 point belts with and without the sub strap and it's more comfortable and more secure in 5 point configuration. Just because it's not perfect doesn't mean it's not worth some effort nonetheless.
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Old 11-15-06, 12:19 AM
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ok since you guys still doubt what i'm saying read pg 26,32 well read the whole thing theres alot of good info that i may have not addresed.

http://www.on-trackperformance.com/S...structions.pdf
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Old 11-15-06, 10:28 AM
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I'm not surprised in the least that Shroth wouldn't sanction cutting your seat, because they couldn't control the quality of the modification in such a variety of applications, and want to protect themselves from liability.

However, other than that all I see are instructions for the mounting angles and such, and a direction not to hang the sub strap over the front, or through the back of a factory seat.

I don't see anything indicating that "foam compression" in the base of the seat is a consideration... and it doesn't make sense: Many aftermarket reclining Recaro and Sparco, as well as some factory seats in Porsches and BMW's that HAVE a sub strap hole built in are padded just the same as any other factory seat. Once you cinch down the belts, you've effectively removed much of the foam give anyway. I remember the first time I cinched my belts down w/ the factory seat, and I couldn't reach the steering wheel anymore.

I don't see any practical reason why a 1/2" x 2" slit cut in the bottom of a seat is really going to be a safety hazzard. I've looked at seats that have the slit built in, and it's not like they've added any massive reinforcement, it's just a hole. The very center of the lower bucket isn't really a high stress area, and is nowhere near the mounting points.

4 pt. belts are a waste of time. If you cinch down the shoulder straps to do any good, it'll hike the lap belt rightup to your ribs. You'd be better off with a $20 CG-Lock (which actually work pretty well). You're far safer with a sub strap mounted at the right angle through a sensible slit cut in the factory seat.
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