3/4 Point Harness Mount Points for Autocross

[LastNightsPants]

Hey everyone, I just started doing auto cross this year and I've started to feel like im forcing my body to stay centered in the seat, so i've been looking at different harnesses.

Originally i was looking at the quickfit from Schroth which was perfect because i use my back seats on occasion, but I have a 2018 and apparently the rear buckles are different so it wont work. So now im looking at other Schroth's and Corbeau's 3/4 point harness, but I'm not really sure where a good place to mount them is in the back. I don't want to really cut anything or weld a plate on the C pillar.

So my though is to use the child seat restraints as the mount point, there's 3 of them in the back seat one at the top and 2 in the seat at about the same level as the seat buckle. The major concern is see is that those child restraint points are probably not as strong as traditional mounting points, but couldn't I just wear the stock seat belt in addition as a backup in case the back fails?

I know this probably won't fly at a track tech inspection, but thats fine I just doing autocross right now so i'm also not worried at all about a roll over. Is there anything I'm missing here for why it wouldn't be a good idea?

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[racrguy]

From a pure safety aspect I would NEVER do a 4 point harness EVER. You can submarine out of them FAR too easily. If you’re having a problem with maintaining body position, your problem isn’t the mechanism that keeps you in the seat, it’s the seat itself. Get something with some bolstering that will hold you up.

Please, for your own safety, buy quality parts that are actually safe. No less than a 5 point harness and a seat that will hold you up. If you’re to the point you need a harness, you need a roll cage.

 

[ahhter]

Hey everyone, I just started doing auto cross this year and I've started to feel like im forcing my body to stay centered in the seat, so i've been looking at different harnesses.

Originally i was looking at the quickfit from Schroth which was perfect because i use my back seats on occasion, but I have a 2018 and apparently the rear buckles are different so it wont work. So now im looking at other Schroth's and Corbeau's 3/4 point harness, but I'm not really sure where a good place to mount them is in the back. I don't want to really cut anything or weld a plate on the C pillar.

So my though is to use the child seat restraints as the mount point, there's 3 of them in the back seat one at the top and 2 in the seat at about the same level as the seat buckle. The major concern is see is that those child restraint points are probably not as strong as traditional mounting points, but couldn't I just wear the stock seat belt in addition as a backup in case the back fails?

I know this probably won't fly at a track tech inspection, but thats fine I just doing autocross right now so i'm also not worried at all about a roll over. Is there anything I'm missing here for why it wouldn't be a good idea?

Not speaking to the Mustang specifically, but last time I installed a 4 point Schroth into an autox car, I was able to use the existing seatbelt bolts in the back seat to install a Rallye4 harness. I don't see why that wouldn't also work in the Mustang.

From a pure safety aspect I would NEVER do a 4 point harness EVER. You can submarine out of them FAR too easily. If you’re having a problem with maintaining body position, your problem isn’t the mechanism that keeps you in the seat, it’s the seat itself. Get something with some bolstering that will hold you up.

Please, for your own safety, buy quality parts that are actually safe. No less than a 5 point harness and a seat that will hold you up. If you’re to the point you need a harness, you need a roll cage.

Seat swapping isn't permitted by SCCA rules in the base Street class that most people run so people have to work within the rules. Running a 4 point harness in autocross is perfectly safe and the popular 4 point harnesses for the sport, such as Schroth, are designed with anti-submarining in mind. Running a roll cage would be overkill, and even unsafe, considering most people daily drive their autocross vehicles and you don't want a full cage in your everyday vehicle where you're not wearing a helmet. Now, if we're talking about a track day vehicle then I agree with you but that's a different situation.

 

[NightmareMoon]

I used the child safety restraint mounts (the rear buckets are already have slits which lead to those points so its an easy and clean install. Schroth Rallye-4 ASM on a 2016 GT

Theres a longer thread in this forum which goes into this in more detail, but the gist is that yeah those mounting points are not probably super strong, so if you take crash safety very seriously you way want to reinforce the existing mounts.

Boy I do love having the harness tho. Soo much less flopping around on course, I can actually focus on piloting instead of holding on for dear life. Too bad even the factory Recaros move around so much. I don’t notice often while driving but the video evidence doesn’t lie.

 

[ahhter]

I used the child safety restraint mounts (the rear buckets are already have slits which lead to those points so its an easy and clean install. Schroth Rallye-4 ASM on a 2016 GT

Theres a longer thread in this forum which goes into this in more detail, but the gist is that yeah those mounting points are not probably super strong, so if you take crash safety very seriously you way want to reinforce the existing mounts.

Boy I do love having the harness tho. Soo much less flopping around on course, I can actually focus on piloting instead of holding on for dear life. Too bad even the factory Recaros move around so much. I don’t notice often while driving but the video evidence doesn’t lie.

Yeah I don't like the idea of using the child safety mounts, they just aren't made for that level of weight. The seat belt bolts should be just off to either side of those child mounts and will be much stronger.

 

[JohnD]

From a pure safety aspect I would NEVER do a 4 point harness EVER. You can submarine out of them FAR too easily. If you’re having a problem with maintaining body position, your problem isn’t the mechanism that keeps you in the seat, it’s the seat itself. Get something with some bolstering that will hold you up.

Please, for your own safety, buy quality parts that are actually safe. No less than a 5 point harness and a seat that will hold you up. If you’re to the point you need a harness, you need a roll cage.

Read up on Schroth's ASM technology. People invent new shit all the time, and new ways of doing old things. All you have to do is follow explicitly what they tell you when you install and use them. For 99% of people doing lapping days this is going to work just fine.

https://www.schroth.com/en/segments/tuning/service/technologie-tech-tip/schroth-asm.html

I don't agree at all with your assertion that if you need a harness you need a roll cage. Modern cars with containment air bag systems and the roll over protection built in are extremely safe and strong. I have absolutely no concerns that I don't have a cage. Bone stock cars like a modern PP Mustang can generate enough side forces as delivered to make a harness necessary and a cage is just not necessary for properly run lapping days.

 

[Grintch]

Read up on Schroth's ASM technology. People invent new shit all the time, and new ways of doing old things. All you have to do is follow explicitly what they tell you when you install and use them. For 99% of people doing lapping days this is going to work just fine.

https://www.schroth.com/en/segments/tuning/service/technologie-tech-tip/schroth-asm.html

I don't agree at all with your assertion that if you need a harness you need a roll cage. Modern cars with containment air bag systems and the roll over protection built in are extremely safe and strong. I have absolutely no concerns that I don't have a cage. Bone stock cars like a modern PP Mustang can generate enough side forces as delivered to make a harness necessary and a cage is just not necessary for properly run lapping days.

+1

In addition I think the submarining risk is very low with a conventional seat, and seating position. Now a layed back formula or sports racer seat yeah, especially when a lot of those seats are poured and held in place with the belts.

But if it makes you feel better wear the regular belts too, then if the child seat mount fail, you still have a seat belt. One with an anti submarine design.
.

 

[LastNightsPants]

+1

In addition I think the submarining risk is very low with a conventional seat, and seating position. Now a layed back formula or sports racer seat yeah, especially when a lot of those seats are poured and held in place with the belts.

But if it makes you feel better wear the regular belts too, then if the child seat mount fail, you still have a seat belt. One with an anti submarine design.
.

Ya that is my thought, if i get a schroth harness with ASM and then where my stock belt just in case the mount point in the back fails ill still be okay. Its just auto cross so risk of a serious accident is already really low.

 

[Grintch]

Hey, now you have an excuse to eat junk food and ice cream. A belly is a built in antisubmarine system. ;-)

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