Alpine951

I just installed some after market sport seats with holes for the shoulder harness. I am doing Driver's Ed with my car which is my no snow street car. my seat does not have a hole in the seat cushion so I have been told that the single sub strap on a 5 point will not work. I don't fully understand why. From what I have found by searching here the sub strap is not necessarily to prevent sliding under the lap belt but its to keep the lap belt low enough on your pelvis. is this correct? I have seen pictures here of the sub straps on a six point attached with bolt ends to the seat front mounting holes in the floorboard. Is this the correct spot for mounting the 6 point sub strap? I was planning to use the outside stock belt attachment with an eye bolt so i could use the stock belt on the street and attach the lap belt here with a snap hook. I am also planning to drill into the tunnel of mt 951 for the inner lap belt, and use a backing plate behind the tunnel. Can these lap belt mounts also be used for the sub strap mounts?

Tom W

You need to check your local rules for what is or is not allowed (in addition to your decision on if it's safe or not). Most rules I've seen prohibit more than one belt being attached to a single mounting point, so you couldn't monut both sub and lap to the same point. It's also likely that the sub will not be long enogh to attach there as they are designed for closer mounting.

My Schroth 6-points had a diagram that showed the mounting of the sub to the floor below and slightly behind the driver. I ended up drilling and mounting two eye bolts through the floor with big backing washers. They are mounted as far forward as the DME under the driver seat permits.

RedlineMan

Hey Alpine -

Although there is STILL constant misinformation to the contrary, you are correct that in a sedan the sub keeps the belt in proper position, not the driver. If you are relying on your sub to keep you in the seat, then your belts and seat are configured wrong and you have more serious problems.

You have been told the single sub will not work if it is run to the front of the seat, and this is "correct." It is sometimes a compromise that is taken, but it is not very effective in the final analysis.

I would indeed recommend you get a six point, and make sure the sixth is LONG!!! You need to run it back and through the split between the seat base and back, and mount it somewhere on the floor. Where you mount it depends on your stature, and whether you want to drill holes.

I am DECIDEDLY NOT a fan of eye-bolt-through-sheetmetal mounting. Sheetmetal is NOT strong enough, and I don't care HOW big the washers are. I have a friend with a 914-6 that did his belts that way. Used 3" washers. Had them for years. Never hit anything, and the sheetmtal was TEARING around the washers!!! Needless to say that when I rebuilt the car for him, I did the belts RIGHT!

Having said that, in the case of a substrap that will not see extreme loads like a main belt, I think it is acceptable.

You will be sitting on the 6-point and it will be functioning similar to a climber's harness. The use of 6 -vs- 5 becomes immediately apparent! It should be adjusted plenty low, to the point that it puts the buckle below thigh level. This seems dumb and annoying until you crank down the shoulders and watch the buckle and lap belt rise to exactly the right height!

jerome951

If your seats are aftermarket, I'd suggest cutting a hole in the bottom (most upholstry shops can do this) and properly mounting a 5 or 6 point substrap.

For a few years I used the 6 point method that John describes. Yes, it works, but can be uncomfortable at times.

Brian P

Can you elaborate on that (what do you mean by doing it right)?

JC in NY

Five point sub is meant for sedans, and six point is for formula cars where you sit on the floor. That said, you can use six point in a sedan also. In any case, you must always run the sub belt through the seat and never over the front of the seat - and it should be fixed to the body of the car (not the seat) within about 20 degrees of the seat slot, NOT running all the way back to the shoulder mount point area.

Your harness manufacturer is clear on this, often stating if the belt is run over the front of the seat or back behind the seat "may result in injury or death". Believe them, they know what they're talking about. Do it right.

Z-man

With my stock seats, I have a 6-point system. The sub-strap is mounted underneath the seat rail towards the front. Is this ideal? No, but like Redlineman said, it is a compromise, since I don't have race seats yet. (That's part of my winter upgrade, however!)

I found my sub-straps are not uncomfortable, and it does keep the buckle at the proper position. You can do the same thing with a 5-point substrap by just attaching the substrap to one seat rail, either side.

BTW, sub-straps are a requirement with an aftermarket harness setup in my region (NNJR) for DE's. A four-point system (without a sub-strap) will not prevent the driver from submarining below the harnesses.

Disclaimer: using a 5 or 6 point harness system with stock seats is at best a compromise. Harnesses are more effective when used with the proper race-type seats that have pass-throughs for the shoulder harnesses and the sub-strap.

Just my $0.42,
-Z-man.

JC in NY

I'm not a fan of racing harness with stock seats. I'd prefer the three-point system with stock seats. That three point setup is extensively designed and tested to work together. Add a racing harness (improperly installed) and you mess that system up completely. A racing harness is designed to operate one way only, with a proper racing seat that has the slots for the harness to pass through - and using the proper mounting points.

Once again, read the documentation and warnings that come with your racing harness. The manufacturer is very clear about what works and what is unaccepatable. Yet, despite these warnings there are so many of us that insist on justifying why our non-standard installation is OK. It's black and white - there is only one way to do it and any deviation should be considered unsafe and unacceptable.

Z-man

While I agree that a racing harness in conjunction with a racing seat is the preferred method, I hardly believe that using such a harness with stock seats is "unsafe and unacceptable." Many PCA regions allow the use of racing harnesses with stock seats, including my own region, NNJR.

Granted, stock seats and racing harnesses aren't AS SAFE and as optimally configured as racing seat with racing harnesses, but they do work and IMHO, are effective. I believe they work better than the stock seat belts. Do I have any imperical proof of this? No, I do not. Such data is rather hard to come by!

BTW: I am not an advocate of using both the stock belts together with racing harnesses: they aren't designed to behave the same way in a 'sudden decelleration event:' racing harnesses are designed to stretch (and absorb some force), while stock seat belts are designed to not stretch (that pendulum thingy locks the belt in place) I question combining two such systems: the results may be unpredictable.

With my setup, (stock seat, Redline Rollbar, 6-point harness with H-straps connecting the shoulder harnesses together) I am more securly positioned in my seat with a 6-point harness than with a 3-point stock belt. Note that I'm also 6'2", so there the shoulder straps have less chance of slipping over my shoulders. The position of the lap belts and buckle are within specs. And while the sub-strap is looped over the front of the seat, I cannot see out that can't help keep me in the proper position! With a stock 3-point system, I am more likely to submarine underneat the steering wheel.

Please note that this is IMHO.
-Zoltan.

Mark in Baltimore

Interesting. I'm not a safety expert by any means, but I have to wonder what would happen to an occupant after the harnesses stretched on the initial impact? Wouldn't the person not be as securely restrained and possibly fall out of the harnesses if a second or third impact were to occur? I know harnesses do stretch upon impact, especially ones that are mounted over a longer distance and a greater amount of webbing; I just didn't realize that the stretch was an assessed part of the safety equation.

Also, other than the obvious benefits of immediate occcupant adjustability, how is the locking inertia reel in street seat belts any different than a properly and securely mounted racing harness?

zffnhsn

I reccomend the six point harness. I went through the same learning curve when I shopped for mine. Fortunately I stopped in at Northstar Motorsports to look at the hardware. I've been very please with the result. My lap and six point harnesses attach to the standard lower seatbelt mounting bracket by means of a special I-bolt, they clip in and clip out. I've seen the same webbing clips used on aircraft. The shoulder harnesses are routed through the harness bar anchoring to the rear seat belt anchors. In any case, the system works well for me because the car is a daily driver. I clip the harnesses in on track days. No drilling, carving, punching holes in the car required. The six point webbing keeps the lap belt low and around my hips from two angles. I like it well enough I may upgrade to six point on my dedicated track vehicle.

RedlineMan

OK... here goes... as quick as I can type/think it on my lunch hour!

I am not an industry specialist. My comments are my own and come from my experience and thought. Since I build, configure, and sell this stuff, I also spend a lot of time THINKING about it. Anyone that chooses to disagree with me is free to do so, and do whatever they want, at their own peril!

Belts are designed to stretch, be they OE or A/M ("aftermarket"). OE belts stretch less because the weave is tighter and the fabric thinner. A/M race belts stretch more, but can withstand more stress with a higher ultimate yield (failure) point. Because they stretch more, shorter is generally better, to a point. You want to allow enough length for energy dissipation, but not impact with interior objects or excursion beyond the limits of your "full containment seat" if you have one.

A/M belts with OE seats can be problematic, especially the shorter the driver is. The optimum is harnesses with race seats (some groups are now questioning this without a roll bar, but that is a separate issue). In lieu of race seats, H-straps are ok, but one has to allow that these only work for one size occupant and may limit your driver/passenger list and choices for our DE purposes. If you have harnesses with OE seats and are nervous, wear your 3-point too. Works fine and should make everyone happy.

I feel a sternum strap is the perfect solution for those who do not want race seats. Some even argue that idea (decapitation), but I think they paying attention to that erroneous open wheel info, and are all wet. This last point brings us to subs.

The more upright you sit, the less "important" a sub strap is. To say that subs are "absolutely necessary" in a sedan is a very common and still prevalent MISAPPLICATION of open wheel thinking. Having said that, they can/do still perform an important function of keeping the lap belt low over the hips.

The sub belt itself will see very little tension in the event of a biff. It also SHOULD see very little if the entire system is configured properly. In that light, I feel that its mounting is "less important" than the main harness. As long as the mounting is solid, with very little slack, and will make sure the lap belt rides low over the pelvic area, then it is doing its job. If you get to the point where your sub is called upon to keep you in the seat, you likely have other more urgent problems. You certainly learn about bruising your gonads!

I know that manufacturers list very specific rules about their products. This is natural, as they seek to limit their liability. That does not mean that certain well reasoned compromises cannot be implemented in order to work around equipment that is not ideally suited to the all out racing for which this stuff is intended. If you do seek such compromises, however, the well "reasoned part" is MANDATORY!!!!!!! If you do not understand how these systems work, you do not have the necessary reasoning.

I myself take one such compromise in regard to subs. I mount them to the seat. I use Kirkey aluminum seats in my cars. I mount them to the seat base because these cars are potentially driven by more than one driver. In that light, mounting the "non-adjustable" sub in a fixed location makes it practically impossible to use for differing drivers. I pay VERY CAREFUL ATTENTION to how I mount them however, making sure the mount is backed be a LARGE washer and is always in SHEAR with the seat base. This allows the belt to function in its strongest state with the least chance of failure. I would think long and hard, and be VEEEEERY careful doing this with a plastic seat!

Again, this is a compromise, but IF the rest of the system is properly installed, the light loads that the sub should see will not overwhelm this mounting IN MY OPINION.

There. That is all I can whip up at the moment. Tons of other stuff here I'm sure, but I gotta get back to the shop!!

ninefiveone

Z-Man - You really should reconsider your sub belt mounting. It's more effective to mount them to the same place as you mount the lap belts, run them under and up through your thighs so that they function like a climber's harness (as John mentioned).

This way you can still use oem seats, more effectively mount the sub belts for their intended funtion (this is the way they're mounted in single seat open wheel cars) and will likely be more comfortable as well.

I think everyone here is agreed that going up over the front of the seat is a less than optimal solution. Particularly since there's a more effective place to mount them with zero drilling or cutting of seats.

Z-man

Hugh:
The plan is to upgrade the seats to race seats that have a hole for the sub-belt.

I don't like mounting the sub-belts to the same location as the lap belt because you are now attaching two safety related items to one bolt. If the bolt shears or fails, there's two points of the safety harness that are now ineffective.

I am not sure yet as to how I will mount the sub-belt with the new seats.

-Z.

Brian P

Umm, if that bolt shears or fails, your sub belts are going to be close to useless in your current setup anyhow.

Maybe I'm a bit clueless on this, but I don't see how having your sub belt attached to the same point would add much in terms of stress. Ultimately, the bolt still has to be strong enough to withstand the forces of your body rapidly decelerating. Whether or not it's two belts or one, it's still the same amount of force.