Seat belt bolt size

[Check 6]

Issues with my neck have forced me to quit tracking my car thus no need for harnesses and my wife would like me to put seat belts back in . The question is

What is the size and thread for the bolt that secures the shoulder harness on a three point belt to the “C” post on an “83 euro spec SC thanks

[donporfi]

7/16 fine thread

[Check 6]

Thank you

[ChrisBennet]

Do you mean the "B" pillar, just behind the seat? It's a special shoulder bolt, made by REPA.

I took a picture and measured it for you.





Hope that helps.

[stownsen914]

Pretty sure I have one of these bolts (new) lying around, in case you need one.

[HarryD]

Originally Posted by ChrisBennet

Do you mean the "B" pillar, just behind the seat? It's a special shoulder bolt, made by REPA.

I took a picture and measured it for you.





Hope that helps.

You can duplicate this by using washers and/or bushes.

FYI, all seat belt bolts world wide are Grade 5 (metric 8.8) with SAE 7/16-20 Threads.

The differences are with the heads (metric vs SAE) and if there is a shoulder present.

[Check 6]

Thought I had two in my “stuff” box but don’t so in need to order two before my belts come in

[GH85Carrera]

It is one of the few parts of a Porsche that is NOT metric. The US DOT specifies that bolt is a certain size on all cars sold in the states.

[HarryD]

Originally Posted by GH85Carrera

It is one of the few parts of a Porsche that is NOT metric. The US DOT specifies that bolt is a certain size on all cars sold in the states.

Actually, it is a worldwide standard. SAE 7/16-20 threads. Details of the bolt Head, length, and shoulder design are up to the individual car makers.

[Walt Fricke]

Did the Euros not come with seat belt retractors? All the US SCs had them. So the connection to the B pillar was a D ring (held by a shouldered bolt like what guys have shown), through which the belt ran. The retractor itself doesn't need a shouldered bolt.

Having shouldered belts can be pretty important. The piece of hardware you attach with a bolt needs to swivel, so that the angles of pull are always perpendicular to whatever - D ring or end piece) is taking the force. That way the nylon belt is loaded evenly across its whole surface, should a sudden deceleration occur. If the piece is at an angle to the pull, all the force will be exerted on an edge of the nylon strap initially, and a force which the whole belt could hold might be enough to rip at the edge, which will proceed diagonally across the belting. This is what happened to Dale Earnhardt (force unevenly distributed, though not due to not having a shouldered bolt).

[Trackrash]

Ironically, 7/16" thread is the same as the 11mm thread, which was used on 911s.

[HarryD]

Originally Posted by Trackrash

Ironically, 7/16" thread is the same as the 11mm thread, which was used on 911s.

Interesting. Is the thread pitch the same as well?

[Walt Fricke]

Gordon - that is not what I have understood. I don't think you can substitute an SAE 7/16 threaded bolt for an M11x something - 1.25 or 1.5. I'll check, as I think I have one of these bolts in my collection.

[Walt Fricke]

Well, it sure looks like 1.25 thread on the metric gauge. And my SAE set had one stamped 1.25, which I hadn't understood as an SAE designation. I realized I had no nuts I knew were M11 for sure, as the ones I had were all from racing seat belt applications like forged eyebolts. The Bosch Automotive Handbook doesn't list an 11.

[creaturecat]

are the proper Porsche bolts readily available somewhere?

[GH85Carrera]

Originally Posted by HarryD

Actually, it is a worldwide standard. SAE 7/16-20 threads. Details of the bolt Head, length, and shoulder design are up to the individual car makers.

It might be a worldwide standard, but the entire planet except the USA and Burma and Liberia don't use metric. I am pretty sure Burma and Liberia have very little influence on world standards.

Like wheels are measured in inches as well. I have 17 inch wheels on my car, not 431.8 mm wheels.

[Kraftwerk]

Try to find the OEM issued bolt. It needs to be quality steel not just similar sized.

[Trackrash]

You can use an 11mm nut on a 7/16 SAE bolt and vice versa. So they are the same size, within manufacturing tolerances, IMO. Perhaps Porsche used some "special" 11mm size? Kraftwork, true, the SAE needs to be at least grade 5.

[donporfi]

Buy it from a Pelican

https://www.pelicanparts.com/More_Info/111857793E.htm?pn=111-857-793E-OEM

[donporfi]

See this post

Bolt sizes for sealt belts