How many people actually mount lap belts to stock hole?

[Earendil]

I'm sort of an average height guy at 5'11, and sit with my knees almost knocking the steering column. Even with the seat forward enough for me to do that, the stock mounting location on a 4 door appears to not be far enough back. The Scroth suggested angle should be 60 degrees off the horizontal



and the Sparco seat hole would suggest agreement. But using the stock bolt hole I get something closer to an 80 degree offset, which also causes a slight twist in the belt as it goes through the seat pass through.

looking at the side, camera facing somewhat down, but held horizontally level.



Looking straight down.



As an aside, the OMP belt also doesn't really fit here. The length on the pull up belts puts the buckle uncomfortably close to the seat pass through.

I'm thinking I'll need to drill a hole (avoiding the brake lines) a few inches rear of the stock bolt hole. The entire internet sees the stock position as such a "well duh" place to bolt the lap belt that I had to ask here what everyone else is doing.

Thanks for any comments or suggestions!

[Earendil]

70 views and no response. Is the question or scenario unclear? Or does no one want to touch this with a 10 foot pole?

No matter how you phrase it, I'll take it as an unqualified suggestion with no liability placed on you :)

[squidrope]

I assume the reason you are installing belts and a seat is for safety. If that is the case, wouldn't you want to do as the belt manufacturer recommends?

[Beej '86 325es]

I recently went through a lot of this and found very limited, specific information on how others mounted their belts. I think a lot of this is because everyone mounts their seat differently. I'm very tall, so I had some challenges.

This probably won't help you directly, but may give you some ideas or give you some insight.

Professionally, I work with private jets. Big elaborate ones. I have had a lot of experience working with aircraft seating and belts. Schroth (now owned by Takata) also makes aircraft belts. The MIL spec webbing used is incredibly strong, good for 16,000 lbs or so. However, everything in aircraft and auto that is safety related needs to be tested, certified, yada yada. Testing of seats and belts is VERY expensive. For aircraft, there are only one or two facilities in the US that can do a certified sled test. There may be more for auto. Results of the test are analyzed and plotted with all kinds of considerations taken for every point of the body. Here's a very basic forward-facing seat test example:
https://www.youtube.com/watch?v=p294N3LzGnc

Schroth has a VERY good installation manual, and VERY specific requirements. While I was harness shopping, I noticed that other manufacturers (i.e. Willans) have very different requirements for mounting a seemingly identical harness. This is most likely because it was configuration that it was tested, and passed. A single sled test for a divan (aircraft couch), can run $50k-$100k. So you can see why belt manufacturers are very specific in their instructions...more installation flexibility means more testing.

Is it absolutely critical you follow the manufacturer's instructions? Probably not. I did. But look at other's manuals and you'll see some variation in angles and distances required for mounting points. Just try to get close.

Here are some photos from my install last month:

[FredK]

I mounted my lap belts with the stock hole, and drilled one on the transmission tunnel approximately opposite of the stock hole. I am 5'9" though, with short legs.

I would follow the instructions. In my opinion, it's just drilling another hole, which you have to do anyway for the inboard lap belt.

[Earendil]

I assume the reason you are installing belts and a seat is for safety. If that is the case, wouldn't you want to do as the belt manufacturer recommends?

Because in my case, the belt manufacturer OMP states that the 6 point belt should only be mounted to stock mounting locations. If it can't be (and what 6 point harness can?) that the user should consult the car manufacturer. Passing the buck at its finest.

Schroth has a VERY good installation manual, and VERY specific requirements. While I was harness shopping, I noticed that other manufacturers (i.e. Willans) have very different requirements for mounting a seemingly identical harness. This is most likely because it was configuration that it was tested, and passed.

You are very likely to be right. This at least gives me the confidence to do what seems right. Thanks for perspective and info on the Williams belts, which helps paint a more complete picture and helps me understand why some belt configurations are passing inspection when they appear to violate install instructions. Seems there is some flexibility in some mounting locations.

I mounted my lap belts with the stock hole, and drilled one on the transmission tunnel approximately opposite of the stock hole. I am 5'9" though, with short legs.

I would follow the instructions. In my opinion, it's just drilling another hole, which you have to do anyway for the inboard lap belt.

True. And I'll probably drill another hole. It's just that that hole is right next to the brake and gas lines, which is a different animal than the transmission tunnel :)

[ForcedFirebird]

They suggest the stock belt location, but they also sell a universal eye bolt to move that location. I have used the following links in the last 4 race car builds (three of them also got passenger seats) and they work great. I shaved the plating off and welded them directly to the floor, rather than using them as a washer. They passed NASA, Chump and SCCA tech inspections.

https://www.pegasusautoracing.com/productdetails.asp?RecID=9412

https://www.pegasusautoracing.com/productdetails.asp?RecID=9309

[Earendil]

They suggest the stock belt location, but they also sell a universal eye bolt to move that location. I have used the following links in the last 4 race car builds (three of them also got passenger seats) and they work great. I shaved the plating off and welded them directly to the floor, rather than using them as a washer. They passed NASA, Chump and SCCA tech inspections.

https://www.pegasusautoracing.com/productdetails.asp?RecID=9412

https://www.pegasusautoracing.com/pr...asp?RecID=9309

They not only sell it, they came on 4 of the belt ends! That is exactly what I'll use, along with thick and wide backing plates to attach them. Still, eye bolts through floor to backing plates is not a "stock" location as they dictate. I'm sure it's just a liability thing, and only being able to suggest the one scenario that they tested to death.

So we have Schroth that says one thing, Williams that says another, and OMP that says only mount to stock locations, but here are a bunch of eye bolts.

[TobyB]

Mine go through the floor, a bit like Beej's. But I made flat plates
out of some flat aluminum, and backed and fronted the bolts.
They sit in recesses in the floor, so that if I go pounding over the curbs there's
less chance I'll pull one by catching it on an edge of something or other...

They're placed so that the belts are at an approximate 45 degree angle.

t