Lap belt anchor point?

Going to install lap belts in the Lincoln. While digging through the forum I found one post that said the anchor point should be level with the top of the seat instead of dropped down behind it.

I couldn't find any other info on the proper angle. Here's the older thread, has a picture about halfway down. http://www.jalopyjournal.com/forum/showthread.php?t=134687&highlight=SEAT+BELT

 

Probably depends on the car, on older ones it's not easy to make the anchor point that high, since the floor is almost flat.

 

Same info from 2 different manufacturers.

 

Thanks, I just found a better version of that. http://www.wescoperformance.com/lap-belts-install.html

 

Thanks for posting that. I needed that info. I see they specify grade 5 bolts. I was going to use grade 8. I would ask what people think of that, but thats sure to stir up too much controversy thats already been hashed here.

 

Grade 5 is plenty strong for seat belts, but there isn't anything wrong with using anything stronger, if you have grade 8 bolts they will work just the same.

 

They tell you grade 5 bolts,because they will stretch before they break.Grade 8 bolts can snap from one shock.

 

If I hit something hard enough to snap a grade 8 bolt from a pulling seatbelt, I have bigger problems than that. If I hit something hard enough to stretch a grade 5 bolt with a seatbelt, I'm sure I wouldn't be alive enough to care about that either.
That's like trying to figure out how dead you will be either way.

 

Either will work ok but remember to reinforce the area that the bolts go through. On the 48 we ran a piece of 3/16 x3 (because that is what we had) flat bar from side to side under the floor. It doesn't have to be that drastic but at least some very large washers to keep the bolts from pulling out.

 

I got mine from Juliano's and the directions say a 70 degree angle from the floor. That's what I went with. I've read other wbesites that say the same when you google search.

I used the Juliano's mounting plates that come with grade 8 bolts. I used some lock nuts on those for added hold downage.

 

False. That's a continually perpetuated myth.



Grade 5 is adequate for the application. Grade 8 would be overkill, but would work just fine.

 

I'm going to go with the mounting plate, looks a lot sturdier then the large washer.

 

70 degrees is what the manuals and the books say, if you think of the stresses involved and the angles at work, the mounting point should be as far back as possible to keep the belt pulling straight back at you as you slide forward in an accident. If the mounting point is closer to vertical, the belt does not start pulling on you until it tightens up as you move forward. Clear as mud right.

 

I was trying to imagine where it hits your body, I felt closer to vertical might just break your femurs instead of crushing your organs.

 

I used 2"x2"x1/4" thick strut plates on the bottom side. Separate from seat mounting bolts, so they aren't holding the same bolt.

 

Here's what I'm working with in the back, think I could use this massive bolt that's already there? I haven't got a chance to really get under the car but I think it attaches the body to the frame. If I used that pillar the giant bolt is on but further up on the angled portion it would be pretty sturdy since it's already two layers of metal, plus I would still use the anchor.

 

That bolt you circled looks like a body mount bolt, I think I would make a new hole with a 1/8" x 3" x 3" plate under it. You really need to have the seat belt attached to the floor pan, not the frame, unless the seat is also attached to the frame. In a bad crash, the frame can separate from the body, the belts have to keep you in the seat. Gene

 

I agree and want to add that if possible to at least spot weld the corners of the backing plates to the pan to add a little extra strength... use fine thread bolts along with spotting the nuts to make installing a one man job. Just my 2 cents worth.

 

I only took a quick glance but it seems the frame runs in a pretty straight line back to front from that large bolt. And if it's not obvious, in the bottom right of that picture is the wheel well.

See the small hole, above it? That's where the seat was attached.

 

I don't know what kind of car you have, or which direction is front to back on your picture. Assuming the "ledge" along the right side of your picture is the kickup under the rear seat? Is the hole to mount the seat the small one just above your circle? I'm picturing your frame running right to left under the large bolt, correct? Many frame locations for body mounts are ears welded to the frame, either to the inside or to the outside of the boxed section. Seldom do body mounts go through the entire boxed section of the frame on older stuff, but its not unheard of.

Usually an open area, with clear access to the floor pan, around the body mount area is a good place to put a seat belt anchor point. You just don't want to use the body mount bolt. Gene