Installing a 5 point seatbelt?

[SleeperZ]

I came upon a Porsche 911 with a blown motor I will be parting out. It has stock seats, and a Simpson 5 point seatbelt with a "Y" shoulder harness that I would like to put into my '78Z. I just read this thread.

 

racing harness thread

 

I don't have a cage, just a TEP rear strut brace. I'm not sure where to mount the shoulder harness - has anyone got any ideas? It probably is not a good idea to mount it to the strut tower (off center to begin with), and I'm not sure the strut brace is strong enough. It looks like the seat cannot accomodate the belt anyway (integrated head rest), but the Porsche had it installed this way anyway...

 

I don't use my car competetively, just informal events, no real racing, and the belt would be nice just to hold me in better. I probably would not use it on the street anyway. Thanks for your input.

[SleeperZ]

bump

[Pop N Wood]

I installed a Simpson 5 point harness in my 240 just as you described. The shoulder harness wraps around either side of the stock headrest and bolts to one of the nuts on the strut tower. I did not put in the submarine strap because I was lazy, but it is not hard to do. It has been discussed in past postings.

 

Not the ideal installation? Probably. But it was very common among the autoX's I use to run with back in LA. The (in my case) 4 point installation definitely holds you down and has to be safer than stock belts.

 

As a side note, the 5 point harness can be in place at the same time as the stock belts. This way I have a retractable single sholder belt for around town and the "4" point set up for racing.

[Drax240z]

There is something I'd like to point out just for general awareness. You guys can put in your harnesses however you wish.

 

[soapbox]

 

But consider that the harness is first a safety device, and secondly something that aids in driving by keeping your body in place. To keep your body in place, nearly any attachment points will suffice. However, as far as a safety device goes, you want to consider carefully where you mount all points of your harness.

 

Ideally, you want your harness attachments to be on the most rigid part of the car, in most race cars this is by far the roll cage. There is a big reason for this. If you roll your car, get T-boned, etc what happens to your car? Deformation to be sure. You can imagine the force that is required to deform a steel car significantly. Now imagine what that force would do to your body, because by attaching your harness to a highly deformable section of your car, those forces will be transferred along the harness to your body.

 

In other words, if you attach to your strut towers in the rear, and get T-boned on the rear axle, your strut tower might move a few inches. If its moving a few inches backwards, you're in for some serious trouble.

 

Another point, don't spread the shoulder harness mounts too far apart, or you'll squeeze between them in a crash. I would say 4-6" is the only range allowed between the shoulder belts at the anchor point.

 

And while I'm on the subject, be aware of the angle the harness shoulder mount makes when it leaves your shoulder. You want it to be between about 45 degrees downward angle, and horizontal. If its going up from your shoulder, its not doing its job. If its at more than a 45 degree angle, you could have serious compression of your spine occuring in an accident.

 

I believe that most of these issues are raised in manufacturers instructions. But you'd be surprised how often in even in open-wheel, open-cockpit car design, the harness is an add-on instead of something integrated well into the design.

 

The 5th point in a harness is a terribly useful one, but can be neglected depending how your harness fits, your seat angle, body shape, etc. Its purpose is to keep the buckle from riding up once installed. It isn't a restraint for your body at all. Personally I'd never buy a 4-point harness, but to each his own. (its sortof like money, once you have a 6 or 5 point, its hard to go back to something less!)

 

[soapbox]

 

Anyway, not to say you guys did something wrong, I just don't want to see people make uninformed decisions when we're talking about safety equipment. (and also I've got a bit of a unique perspective on this these days)

[Pop N Wood]

Thanks for the sage advice. I agree with all points.

 

But just wanted to point out that I don't have a cage in my car and I do not use the 5 point harness on the street. (I have the submarine strap, just never bothered to hook it up)

 

All I used the harness for is autocrossing (if that is the correct term for individuals racing through cones for time). In these races speeds rarely went over 50 MPH and the only real chance of collision was probably a roll over. Even then, you would have to be doing something extraordinarily special to accomplish that. This was the set up most of the guys in that circuit used. That is why I went that route.

 

If I ever get serious about racing again, I will more than likely pick up a racing seat with the proper shoulder cut outs. But even with that, the options for anchoring the shoulder straps are limited without a cage. That strut bolt is just too conveniently placed!

 

If mounting to a cage, it would have to be a true cage that is well mounted and properly crossed braced. Attaching it to a bolt in roll bar is probably worse than the strut tower.

 

Even with all of the above info, I can't help but wonder whether a harness attached to the strut tower is better or worse than the stock belts. I hadn't thought about someone relocating the strut tower. But either way, it would have to be a pretty severe accident to make a difference.

[SleeperZ]

I appreciate the input, thanks. I shall retain the factory belt to use on the street (it's so much easier to fasten), and use the 5 point on the track or strip - much less chance of an accident there.

 

Of course I am knocking on wood I don't get into an accident on the street; without any bumpers, I don't have much protection (shudder to think about the fuel tank behind me).

[Guest Anonymous]

One more point I'm not sure was brought up, harness like baked goods have shelf life, if your harnesses are old, replace them, the elements screw them up and deteriorates them, so watch manufacturer dates and change them according to manufacturers sugestions, you'll thank yourself when they stop you from going through the windshield.

 

Regards,

 

Lone

 

Ps: This goes for old seatbelts too, leave the ones at the wrecking yards and get new ones if you havn't, its not worth dying over a hundred bucks or so.

[Guest gprix1]

That has always made me wonder. If your supposed to replace racing harnesses so damned often, why do we keep our factory seatbelts for 20 years 200k miles? I mean is there something inherintly wrong with racing harnesses that make them not last as long or is it that people use factory harnesses way beyond their useful life? If that was the case you'd think the DOT would be all over that one.

 

Things that make you go hmmmmm..