Racelabz did a welded 4 point bar for me about a year ago, and I am having them do a full cage now. I'm very happy with the job they are doing, but have a lingering quesiton...

As it stands now, the harness bar is about 10" behind the rear of my seat. It seems hard to find definitive information about whether or not this is "too" far away from the seat, ie there is extra belt that would stretch during a crash. What I have found are some references to minimizing the distance between the shoulder harness mounting points and the drivers shoulder, and a recommendation of 200MM or less in the Schroth harness install guide.

My question is, is it worth having a second harness bar welded in either in the same plane as the main hoop or slightly back from it so the distance between the seat and the harness bar is minimized? Do I need to worry about this or just be happy with what I have? I've been told by a few folks that 10" is not a big deal.

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anyone?

 

Matt I would go with the mounting instructions from Schroth. The guidelines in the NASA CCR are not as clear. If you use a different belt than Schroth then go by their guidelines. I have notices different measurements regarding the angle of the shoulder straps from you shoulders to the mounting point to be different from each manufacturer as an example.

On a different note, now that you are caged are you going through comp school?

 

seat belts stretch some number of inches per foot of belt in an accident. So shorter is better, but I don't think the couple inches you're asking about make a difference. If it were "feet" extra I might ask them to do it better.

 

I wouldn't worry about it. I intentionally placed the harness bar in my cage 8" behind the drivers seat. From reading the Schroth pdf and other sources, the angle from the seat hols down to the bar is more important than the length. Every person and seat combination will make for a different shoulder height, and having a little bit of distance between the seat back and the bar makes the belt angle less sensitive to seat height.

 

Thanks for your comments folks. When all was said and done, there ended up being 8.25" between the seat and the bar after getting the seat on its new fixed mounts. I called HMS Motorsport, the US Supplier of Schroth, and they said that 8" or 10" is completely fine. They said you need to start worrying about belt elongation with a lot more belt, like 32."

So, I left the harness bar where it was. As mentioned above, this does decrease any angle between the seat harness holes and the bar, which is very important for safety.

Rob, I do plan to do comp school later this year. Right now we are trying to get the lemons car ready for a chumpcar race at VIR, so I'm not really thinking about when I can do comp school. Maybe this summer.

 

 

Great placement. Good suggestions here as well. Definitely read that Schroth guide!