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Discussion Starter · #1 ·
Is this safe? I've heard that If the mounting point isn't above your shoulders or equal to them it will compress your spine in a collision. I'd put a roll bar in but I don't want the back seat to be out of commission.
 

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It's true that mounting the shoulder belts to the floor can compress the spinal vertebrae in a crash. The angle of pull is all wrong. Shoulder belts should be mounted even with the shoulders to a maximum of 4" below the shoulders. Also, pay attention to the crotch strap mount. DO NOT attach it at the front of the seat. See the attached photo for proper 5-point belt installation.

If you want to use shoulder belts without a roll bar/cross bar, then rig up a mount back at the shelf panel (package tray).
 

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Discussion Starter · #3 ·
That would still make the back seat unusable. At the very least inconvenient to sit it. If I get an aluminum seat from Kirkey or something could I weld blocks on to the back of the seats then drill and tap them, then bolt the belts to the seat?
 

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Tomlowe523 said:
If I get an aluminum seat from Kirkey or something could I weld blocks on to the back of the seats then drill and tap them, then bolt the belts to the seat?
Having the belts anchored to the seat is not legal. The best way would be to have them anchored to the required cross bar. This from the NHRA rule book: "Sidebar must be included on driver's side and must pass the driver at a point midway between the shoulder and elbow. Swing-out sidebar permitted. All roll bars must have in thier construction a cross bar for seat bracing and as the shoulder harness attachement point; cross bar must be installed no more than 4 inches below, and not above, the drivers shoulders or to the side bar." There are more regs on bracing etc, so I suggest that you get a rule book and look up 4:10 ROLL BAR on page 261.
 

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I didn't mean to suggest that shoulder belts mounted at the package tray were legal to go quicker than 11.50. I thought this was just a street car that he maybe wanted some extra protection in. A simple lap belt is all you need down to 11.50, but at 11.49 and quicker you need the 5-point belts installed per the photo I posted.....with a roll bar or roll cage.
 

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He's 17. That back seat could be the geographic focus of his existance. :mwink: But the idea of having the 5-point belts is still good, both from the safety perspective as well as the image perspective.

Is the car a 2-door? 4-door? Is it yours (are you free to modify it without getting in big trouble)?

Pat
 

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Discussion Starter · #8 ·
Its a 77 Trans Am. By law its my dads, I'm only 17, I can't have a car in my name, but yes I'm free to make modifications to it. It is already modified to a certain extent, it has a built 455 in it. Weight reductions such as the front bumper is gone, the A/C compressor, condensor, blower motor,etc.
 

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If you plan to be in a situation where you actually need a 5 point harness, you need more framework than a 1977 unitized body has to offer.
And the sheetmetal floor, is not a good attachement point.

Now, with proper framework and a rollcage, the 5 point harness can be properly installed without rendering the back seat useless. (albeit the back seat of a '77 firebird, was pretty much useless anyway, unless yer both small people, ;) )

Thanx
Shorty
 
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