Replacing seat belt anchor bolts with harness eye bolts?

Replacing seat belt anchor bolts with harness eye bolts?

Author
Discussion

TroubledSoul

Original Poster:

4,599 posts

194 months

Tuesday 4th July 2017
quotequote all
I'm just looking into this so that I can fit a harness to my road legal track car. Are the bolts for seat belts a standard size or do I need something specific to a Subaru?

I've seen these:
http://www.ebay.co.uk/itm/4-x-RSA-Harness-Seatbelt...

Would they by the kind of thing I should buy?

E-bmw

9,220 posts

152 months

Tuesday 4th July 2017
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I have no idea why (I am sure someone will be along to tell us) but for some reason they are all 7/16 UNF across the world (I have never come across any different anyway), so they will be fine.

CrutyRammers

13,735 posts

198 months

Tuesday 4th July 2017
quotequote all
Harness bolts are standardised at 7/16 UNF. I don't know what production cars use though; I'd take one off and measure it. But assuming the same thread, then yes, that's exactly the sort of thing. Eyebolts from a recognised supplier like JCC should be to spec, but if you go with a small supplier, check that they are motorsport approved, or that they are 12.9 High Tensile grade.

From what I remember most harnesses use eyebolts; a few don't though so check before you buy. I think anything FIA approved will.

TroubledSoul

Original Poster:

4,599 posts

194 months

Tuesday 4th July 2017
quotequote all
Well I was trying to find stuff that doesn't but the majority do and this seems the easiest route in all honesty. It also means I can fit the bucket seat on the passenger side and fit the harness later as it will be easy if the eye bolts are already there thumbup

E-bmw

9,220 posts

152 months

Wednesday 5th July 2017
quotequote all
Just make sure you check the mountings as there are many with flat plates with holes in & many that use eye bolts to fit.

FWIW I am about to fit harnesses to mine but will be leaving the original belts in for road use, so I am getting eye bolts to replace the original bolts & will fit the harnesses only when on track.

TimCrighton

996 posts

216 months

Wednesday 5th July 2017
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Harnesses are standardised as said above using a UNF thread and not a metric thread and the UNF pitch is much better and therefore more resistant to the tension it undergoes as a harness anchor point.

Just the same as many of the major race car manufacturers use UNF threads within their chassis and on key suspension components as the thread pitch is much preferable.


TroubledSoul

Original Poster:

4,599 posts

194 months

Thursday 6th July 2017
quotequote all
Cheers folks. At present, I too intend to keep the seat belts for road use, hence looking at the longer eye bolts. Just not sure how long is right so I'll have to go trial and error I think.

loggyboy

279 posts

178 months

Thursday 6th July 2017
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Being french - the Clio used a mix of M10 and UNF for the seat belt anchorages which meant a mix of bolts when doing mine!

nickfrog

21,160 posts

217 months

Thursday 6th July 2017
quotequote all
I use the original belt hardware in the Megane but I have added these for the harness http://www.barrabes.co.uk/petzl-coeur-steel-12-mm/...

It's a well proven solution on track days but NOT an official one - I decline any responsibility of course. You should ideally have a cage with harness too.

http://www.meganers.fr/phpBB3/viewtopic.php?f=50&a...

Photos here for the rear bench install BUT I have used the actual belt mounting points at the front.


gcpeters

961 posts

232 months

Tuesday 8th August 2017
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nickfrog said:
I use the original belt hardware in the Megane but I have added these for the harness http://www.barrabes.co.uk/petzl-coeur-steel-12-mm/...

It's a well proven solution on track days but NOT an official one - I decline any responsibility of course. You should ideally have a cage with harness too.

http://www.meganers.fr/phpBB3/viewtopic.php?f=50&a...

Photos here for the rear bench install BUT I have used the actual belt mounting points at the front.
is that not a bit dodgy as they have the "lap belts" of the four point harness's bolted to the seat mount?

1781cc

576 posts

94 months

Wednesday 9th August 2017
quotequote all
Please be careful with the angles on your car, most harness manufacturers advise against angles that are too low on account of resistance and force applied if in a crash



A better option might be your equivalent of one of these which are specifically designed for the purpose:


loggyboy

279 posts

178 months

Wednesday 9th August 2017
quotequote all
1781cc said:
Please be careful with the angles on your car, most harness manufacturers advise against angles that are too low on account of resistance and force applied if in a crash



A better option might be your equivalent of one of these which are specifically designed for the purpose:

You picking and choosing mixed messages there. If one is dangerous then so is the other.
MSA recommend 20 degrees from Horizontal, but that 45 is acceptable, so I work to that, safe in the knowledge a harness even, not in its optimum position will be much better than a 3point seatbelt.

TroubledSoul

Original Poster:

4,599 posts

194 months

Wednesday 9th August 2017
quotequote all
Yeah you do have to be careful. My understanding is that the wrong angle is going to compress your spine in an accident and that can only go one way....

1781cc

576 posts

94 months

Wednesday 9th August 2017
quotequote all
loggyboy said:
You picking and choosing mixed messages there. If one is dangerous then so is the other.
MSA recommend 20 degrees from Horizontal, but that 45 is acceptable, so I work to that, safe in the knowledge a harness even, not in its optimum position will be much better than a 3point seatbelt.
I was just trying to say that rather than tether something to mounting points that are existing and adding eyes into the equation, which isn't ideal, especially if the angles of the eyes aren't aligned where they need to be if they naturally reach the end of their thread tightening, (they will have to be adjusted using washers until they are) but if thats the way the OP wants to go, it might be worth looking at something thats designed to make use of the existing setup.

I'm not trying to argue that either option is safest, because in reality a harness bar is the safest and thats not mentioned as an option.


TroubledSoul

Original Poster:

4,599 posts

194 months

Wednesday 9th August 2017
quotequote all
I am using a harness bar, but the harness is clip on so I'm replacing the lap belt seat belt bolts.

Steve H

5,283 posts

195 months

Wednesday 9th August 2017
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Save yourself the messing and just get a CG Lock - http://www.demon-tweeks.co.uk/performance/harness-...

Quick to fit, effective at holding you in the seat when cornering and has the added advantage of not snapping your neck if you manage to roll the car and the roof comes in as is the risk if you have fitted harnesses but haven't fitted a cage.

Harnesses, seats and cage really should be looked at as one package.

Ekona

1,653 posts

202 months

Thursday 10th August 2017
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CG Lock isn't even close to what a harness can do (I use both across different cars), but more importantly you can't get CG Locks any more as they've stopped making them. I have no idea why, as they were a brilliant idea and did a job very well.

So yeah, mine is now available for £500 wink

Steve H

5,283 posts

195 months

Thursday 10th August 2017
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I didn't realise you couldn't get them any more, shame cos it's a good piece of kit.

i wasn't trying to suggest it was as good as a harness, just that a harness on it's own can do more harm than good in some circumstances and I wouldn't recommend using them without a cage.

Robmarriott

2,638 posts

158 months

Friday 11th August 2017
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I'll bite. Why would you not use harnesses without a cage?

1781cc

576 posts

94 months

Friday 11th August 2017
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You can use a harness without a cage, as long as your angles are correct, otherwise, as mentioned above, it can compress your spine and worse.

Benefits of a harness over a seatbelt is that you are more stripped into position, less movement of your body when cornering, less injury through the dispersal of force should you have an accident, etc...