Scroll down to the middle of the page :
https://simpsonraceproducts.com/pdf/inst/Seat_Belt_Mounting.pdf

Some of you guys just give plain scary incorrect advice, my guess based on nothing more than your opinion.

I have built 6 sec Pro-Mods JCC and they pass tech. Because I do what the rulebook and belt makers say. See the link above for how Simpson says to mount their belts.....either level or below shoulder line, which is EXACTLY what I said. Hans or not, the angle is still the same but changes the relative shoulder placement, because of the added height. But I guess Simpson has no clue either. Is that what you are saying JCC?

According to you, block makers, the NHRA, SFI, chassis builders, belt makers and about everyone else has no idea what they are doing. Apparently all they need to do is call you and you could solve all the problems.......Hell, maybe you should run for president and fix that mess as well

I have just fitted this seat to my sons street strip car, just setting it up but the hole for the belts in the seat is way to low.

I always thought the lap belt keep one from going up and foward, shoulder belts keep the upper body from going foward. The lap belt being the most important part. But I can see the belts should be custom fit for each driver, not one size fits all. Glad this post came up, now I know a little more when I put my belts in, thanks

I believe you have the most correct understanding. Shoulder harnesses do a very poor job of restricting any upper body motion other then forward. A well designed racing seat restricts the other directions much better, Surprised a racing seat manufacturer doesn't plainly state that. I also believe one if the reasons the "Y" shoulder belt was no longer approved is, in a sideways incident, the Y shoulder harness induced a lot of forces on the neck in trying to restrain sideways body movement. the neck is not a good place to apply force to restrain body movement. Same applies to our typical shoulder harness today. The Lap belt is the key component here.

The BUtler quote also mentions the submarine belt purpose. Consider, if a typical belted driver weighs 200lbs, the upper torso/head has approx 40%? of the upper body mass restrained in a forward direction by the shoulder harnesses, or 80lbs. In a 10g forward impact, that stresses the two shoulder harnesses with 800lbs of force. Assuming no frictional loss going over the shoulder, that means ea end (4) of ea shoulder harness sees 200lbs of force during the impact. That means the lap belt has additional forces pulling up (parallel to to the spine?) of 400lbs. If the lap belt is mounted at its intended angle, the lap belt wants to rotate upwards with this lower shoulder belt induced force. The abdomen, above the pelvis, is very delicate with a lot of fragile organs, and a dangerous area to impact. That upward movement is mainly resisted by a properly positioned "submarine" belt. IMO a submarine belt is mis labeled for upright seating.

CMcAllister, pic is a bit deceiving, seat position is great, top of rear bar is only about 1" below shoulder, just the hole in seat is low, we are not tall guys either. is it a big NO NO to have the belts over the seat as in the pic ? when strapped in it feel good.

I went to the other post on proper seat belt position and read the FAA guidelines from the test they did. Very interesting read, good pics, same as what you're saying, crotch belt is very important in keeping the other belts, and the person, in the right place. NHRA rules have been out a long time and I don't know if they're up to speed with the new info of today. I mean, who has more money and clout, NHRA or the FAA to do all the test?