Anti-sub Seat Belt

[Blue MK3]

My MK3 is equipped with a Simpson 4-point harness. I plan to install an anti-sub belt soon. The AS belt would probably add some additional security, but the main reason for adding it is to prevent the lap belt from being pulled up when the shoulder belts are snugged. My question is where to attach the AS to the floor/frame. The mounting location that appears most convenient and comfortable is somewhere into the aluminum floor panel, although that doesn't seem like the strongest location. I guess I could mount it into the X-frame tubes under the DS seat, but I'm reluctant to drill a hole in the frame. My inclination is to mount it into the aluminum, since I currently have NO AS belt support and anything would be an improvement. Also, preventing the lap belt from riding up would offer even more support/safety. Any suggestions?

[MPTech]

Don't know if it helps you, but the mk4 comes with a 5-point harness. I just mounted mine a couple weeks ago, just under the front of the seat (I heard it's better if the seat has a sub slot, but it is what it is). The mk4 floor has a steel plate under it, a revision from the mk3.1 x-tubes. Could you fab some kind of plate or brace that ties into the x-brace? I would think that's the best, but as you said, anything is an improvement and I don't think it takes the full brunt of the strain in an accident, more to hold the lap and shoulder down.

One tip, measure carefully before adjusting the sub-strap length and bolting the seats back in. Mine is a real pain to reach after the seats are bolted in and the strap was too short so I had to un-bolt the seats, adjust the strap, and re-bolt the seats. :cool:

[ram_g]

The mk4 floor has a steel plate under it, a revision from the mk3.1 x-tubes. Could you fab some kind of plate or brace that ties into the x-brace?

The Mk3.1 has a steel plate between the cross-tubes as well, no need to fab anything. Agree this is where the sub-strap bolts on to.

[Blue MK3]

Thanks. I'll crawl back under the car or jack it up to get a better view of the underside. If there's a steel plate there, I didnt notice it. Attaching to the plate would make for the best solution. More later.

[Blue MK3]

Thanks, ram. I jacked the car up for a better look and you are correct in that there IS a steel plate welded into the frame under the seats. This will simplify matters a lot. To paraphrase Yogi Berra, "You can see a lot by looking." ;)

[ram_g]

Blue, if you've never accessed mk3build.com I suggest you do (need to register but don't need to pay anything). It's a great build site; I was reminded of it because it has precise instructions for where to drill the sub belt locating bolt hole amongst all kinds of other useful tidbits.

[Blue MK3]

I'm registered now on the mk3build site and see how and where the AS belt is installed. Thanks a bunch, ram.

[CraigS]

Now that you got the info on the install I'll add my thoughts on it's use. You are corect in thinking it is mainly for keeping the lapdown from riding up. If there were a hole through the seat it could have more of an anit-sub function, But w/ the pretty upright position in an FFR that really isn't needed. I like to get all the belts attched at the buckle and start by tightening the lap as tight as possible. Then I do the same for the sub. Finally I tighten the shoulder belts. I find this tightening order to enhance the 'don't let it ride upward' function.

[Blue MK3]

Now that you got the info on the install I'll add my thoughts on it's use. You are corect in thinking it is mainly for keeping the lapdown from riding up. If there were a hole through the seat it could have more of an anit-sub function, But w/ the pretty upright position in an FFR that really isn't needed. I like to get all the belts attched at the buckle and start by tightening the lap as tight as possible. Then I do the same for the sub. Finally I tighten the shoulder belts. I find this tightening order to enhance the 'don't let it ride upward' function.

Thanks. I'll see how the adjustment works out once the AS belts are installed. I have MK4 seats in my MK3, but don't know if that will make much difference. I also have a pair of the FFR high back racing seats that came along with the car. They have slots in the back for the shoulder belts, but nothing in the seat cushion so there's no advantage there. I'm thinking of getting rid of them, even though my wife likes them.

[tirod]

Actually, the anti submarine belt keeps you from sliding out from under the seat belt during a high speed impact.

Got to teach an auto course at the high school level a few years ago, buddy teamed with a Firefighter trained in collision rescue. He had numerous hours in training, and all too many numerous hours in actual rescue. One part of the curriculum was a bit of real world "What happens in an accident?"

At about 45mph and above, inertian forces you to slide out from under the seat belt, your knees hit the firewall, and whatever part is still supporting your body weight folds in half, trapping you under the dash board. At least these days the engine goes under the chassis, not straight back at you. His experience was to manuever the jaws of life in and around the dash to remove it and get the trapped driver out from under it.

The anti sub belt was added back in the '60s as a race safety item to keep you in the seat a bit more. Considering that the force of impact can fold your leg bones and create two new knees, it might be the better thing. The pelvis is considerably stronger. Makes sense, it's really no different than parachuting - you don't want to come out of the harness.

However, in the day at the Infantry School, I got to talking to Airborne students, and the anti sub straps on the harness were no joy, either. But, they are the lesser of two evils by a large margin, I'm told.

The method I see now recommended is a dual anti sub strap, which lessens the single point load on the pelvic girdle. http://www.circletrack.com/techarticles/ctrp_0710_seven_points_of_safety/viewall.html

In any case, something is better than nothing. Assess your risk. Pay close attention to how these belts are supposed to be routed, lap belts aren't positioned above the hip bone. http://www.schroth.com/installation-instructions/en/03_anchorage_locations_and_geometries.htm

Did I read over 4,000 pounds of pelvic load? Mom can't hold a baby in her arms during an impact, either, which is the point to child safety seats.

[Blue MK3]

That's an interesting read, tirod. However, in light of the layout of the FFR car and seats, it looks like the best I can do is install the crotch strap and hope for the best. As stated, it's better than what I have, which is nothing. I'll just have to take my chances about becoming a soprano. :)

[Someday I Suppose]

Blue, as noted how effective the sub is will depend a bit on how much room you have between the front edge of the seat and your body. For us bigger boned people I think it works fine on the FFR, I know some smaller people have cut a hole and moved the slot back so it is closer.

As for other options, I believe Stroh makes a 4 strap cam lock belt with anti-sub technology that a few people have used as well. Some really like the cam lock for ease of use, but I think there is something cool / vintage with the simpson latch.

Scott

[Blue MK3]

Scott, I'm small boned and don't weigh a bunch. So I guess my chances are higher at becoming a soprano. Nothing I can do about it. Cutting a slot in the seats is not an option. I'll just add the AS belts and drive carefully.

[tirod]

Considering how much gets spent on kit accessories, cutting a hole in the seat isn't much. It's really a matter of whether a street car needs them at all, as the risk of going head on into a solid object at 110 is much less. Track car builders put the mounts where they need to be, which is another finesse point during the build of a street car.

Like a lot of other safety equipment, the suppliers will strongly suggest that doing it right is as important as doing it at all. A poor installation could possibly increase the severity of injury. I'd rather not be in the position where I have to watch the Sopranos on the hospital room cable TV. I'm sensitive to toxic levels of irony.