3" vs 2" seat belts... surprising information on that

Jerry Bransford

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In addition to the factory 3-point seatbelts I use 99% of the time, I installed 3" lap belts and 2" shoulder harnesses years ago. The 3" aircraft style lap belts felt good as they spread the load out a bit more. I especially wear the 3" lap belts when the trails get uneven enough to keep locking up the factory seat belts.

Then the evidence came in that the 2" belts are far safer.
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This information was surprising enough to me that I thought it worthwhile posting up here. The article can be read at https://www.onedirt.com/tech/chassi...h-lap-restraints-safer-than-3-inch-lap-belts/
 
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Good information on a really important topic. Most people don't give a second thought to the positioning of the belt. They are designed to be positioned on the hip bones (iliac crest). If the belt is worn above it can do very serious damage during an accident. The forces, even in a low speed accident, are incredible.
 
Great info as I am about to purchase harnesses
Make sure you install the shoulder harness support bar behind the seats at the correct shoulder height. Not doing that part of the job can produce serious consequences, it killed a friend of mine and blinded her husband in the same accident. Her spine was crushed in a slow-speed offroad accident, his leg was broken. Particulates from his broken leg made it up to the blood supply for his optic nerve, blocking its blood supply and killing it, blinding hlm several weeks after the accident. A very sad situation from him not knowing how to properly install his buggy's shoulder harnesses.
 
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That is awful. Yeah I had to order the plus 4” height seats so the slots would be at the right height for my shoulders so I’ll make sure the harness bar is correct as well.
Make sure you install the shoulder harness support bar behind the seats at the correct shoulder height. Not doing that part of the job can produce serious consequences, it killed a friend of mine and blinded her husband in the same accident. Her spine was crushed in a slow-speed offroad accident, his leg was broken. Particulates from his broken leg made it up to the blood supply for his optic nerve and blinded him 6 weeks after the accident. A very sad situation from him not knowing how to properly install his buggy's shoulder harnesses.
 
I worked for this company for a number of years before I retired out of the professional racing game. It's solid info on belt mounting relative to shoulder harness height- There are many other references available on the matter. Shoulder belt anchor mounting is one of the my "pet peeves" that I see done wrong so very often, even in the professional ranks. https://www.butlerbuilt.net/Content...-pdfs/Proper_Seat_Belt_Mounting-Stock_car.pdf I often see folks bolting shoulder belts to the floor and having the strap come up and over. If you want to get folded in half and your spine compressed during it, that is a great way to do it. Unfortunately we saw that all too often.
The other big kicker in the offroad game is folks with roll cage components/cross bars too close to their head. Your melon weighs a whole lot swinging around on your neck during a rollover, the last thing it needs to do is smack part of the cage after developing any sort of speed.
 
I... often see folks bolting shoulder belts to the floor and having the strap come up and over. If you want to get folded in half and your spine compressed during it, that is a great way to do it.
That is exactly the issue that killed a friend and severely injured/blinded her husband.
 
That is exactly the issue that killed a friend and severely injured/blinded her husband.
I saw that in your reply, I cannot tell you how many times I saw that type of install. Euro Rally racers are just as bad. Typically the belts will run back, in a sedan mind you, from the cockpit area all the way back to the rear "package shelf" where we put our 6x9 speakers when we were younger. The belt stretch alone would have their heads halfway through the dash before pulling up tight.
Safety is no joke, and it (racing safety equipment design/sales) took me around the world preaching it so I'm thankful for the opportunities it provided but i wish common sense were just a bit more "common" or I'd not have seen some of the stupid things that I have through the years and we'd not have lost so many to such simple matters.
 
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Make sure you install the shoulder harness support bar behind the seats at the correct shoulder height. Not doing that part of the job can produce serious consequences, it killed a friend of mine and blinded her husband in the same accident. Her spine was crushed in a slow-speed offroad accident, his leg was broken. Particulates from his broken leg made it up to the blood supply for his optic nerve, blocking its blood supply and killing it, blinding hlm several weeks after the accident. A very sad situation from him not knowing how to properly install his buggy's shoulder harnesses.


Also how you attach to the harness bar is important, welding tabs is a no no, welded bungs or wrapping the bar are the only acceptable ways.
 
This is awesome , this needs to morph into “ this is how to do it thread “ and “how not to” with pics


Not trying to assign anyone a job, but ICDGary and Jerry could save some lives with this.
 
The lap belt holds your hips in the seat.
The shoulder belts keep your body from falling forward.
The "noose" keeps yer noggin steady.

But the shoulder belt, 1 or 2 MUST not compress your spine.
The anchor for any shoulder belt MUST be higher than your shoulders.
The straighter the line from the waist anchor to the ceiling anchor the better.

The geometry is absolutely critical.
It is so freaking simple
 
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Its funny on how different that DOT vs FAA view the function of a seat belt, in auto's it is designed to reduce the force of the impact, in airplanes, they are designed to contain the body...in the event of an accident. That came straight out of the FAA's mount at a seminar on shoulder harnesses.
 
Its funny on how different that DOT vs FAA view the function of a seat belt, in auto's it is designed to reduce the force of the impact, in airplanes, they are designed to contain the body...in the event of an accident. That came straight out of the FAA's mount at a seminar on shoulder harnesses.
Automotive seat belts have always had one of their main purposes intended to keep the occupant inside the vehicle, preventing them from being ejected. The FAA is not the sole adherent of that particular and very basic purpose of seat belts.

Read the #1 point on the NHTSA's web page on the purpose of seat belts. https://www.nhtsa.gov/risky-driving/seat-belts
 
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Pretty simple general knowledge. if you exit/eject from a vehicle in motion, you are fucked.
Thankfully seat belts, air bags, structural integrity have evolved since that 1960s basic instinct.

The after market is just waiting for a multi million dollar lawsuit.

Dale Earnhardt was killed because of that idiotic attitude. Ignore it and die.
 
NHTSA changed the requirements a few decades ago, automotive seat belts are now supposed to reduce impact forces and not just contain the body.
 
On those Euro racers, they all have a cross bar guide behind the headrest.

But really, why use Euro racers as our standard?
How does this even rate as a response?
This is about safety in a TJ.
While some may have a cross bar "guide", the fact remains that elongation of the strap (due to the long run) makes for an unpleasant and abrupt stop as the face plants in the steering wheel. To put the arrangement into perspective, imagine anchoring your TJ shoulder harnesses to the spare tire carrier. You can "guide them" over the shoulder at the right height but the stretch will negate any benefit from having them on.
And it is relative to safety in a TJ because physics and human anatomy are no different in Moab or Johnson Valley than they are at Nurburgring or Daytona or the local bullring dirt track. People can hurt themselves by setting up what they think will provide safety when they do not use the devices correctly.
 
The lap belt holds your hips in the seat.
The shoulder belts keep your body from falling forward.
The "noose" keeps yer noggin steady.

But the shoulder belt, 1 or 2 MUST not compress your spine.
The anchor for any shoulder belt MUST be higher than your shoulders.
The straighter the line from the waist anchor to the ceiling anchor the better.

The geometry is absolutely critical.
It is so freaking simple
Apparently it isn't so freaking simple to some of us because your comment about how the shoulder belt MUST be higher than the shoulders is 100% dead wrong. That's how you break necks and squirt the drivers remains outside the containment envelope of the harness system.

Waist anchor?? Ceiling Anchor?? We aren't docking ships here.
Drivers body type controls lap belt geometry and angle of retention but generally you're going to run in the 60-70 degrees (off horizontal) unless the driver is morbidly obese.

Common knowledge in the racing industry is 0 degrees above to 20 degrees below the shoulder, ANYTHING above dead level cannot control the body in lateral movement, too far below and you risk spinal compression. If using a HANs or other form of head/neck restraint then fine tuning for that specific device comes into play within that envelope.

It really IS so freaking simple, but let's leave it to the individuals to ask true experts instead of someone who apparently didn't stay in a Holiday Inn last night.
 
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