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Seat Back Strength - Racing Harness Ready?

Hello everybody!

Sorry if this is the wrong place to post this, it just has to do with Motorsports so I thought here would be a good place!

Just recently obtained a performance model 3 and was hoping to take it to the race track as soon as possible. I strongly prefer to use a head and neck restraint and unfortunately, unless you purchase a Simpson Hybrid S for about $1000, there are no safe, tested HANS devices to be used with a 3 point belt system.

I reached out to Schroth Racing, a well respected name in Motorsports who offers certified 4 point belt systems that can be used with stock seats, and currently they have no current plan to release a system for the Model 3. However, a few Model 3 owners (one of which is winning many autocross events!) are using a BMW Schroth harness with the stock Model 3 seats to great success. I reached out to Schroth on what could go wrong by doing this. They said that by far the biggest concern is the seat back strength which they actually physically test on the cars before they release a model for that car. Since, I am a bit of a cautious person this worried me a little bit. I know there are some actual tesla engineers here so I was hoping maybe I could get some type of confirmation on the seat back strength. I believe the loading is in the vertical direction and is dynamic in the case of an accident the harnesses kind of slam down on the seat back, keeping you very secure. In most modern cars seat back strength is no issue, but we are talking about a huge amount of loading here.

If anyone knows of a better place to ask this question and potentially get a more accurate answer, please let me know! I would love to use this car to its fullest ability with minimal modifications and maximum safety. Thank you so much for reading!

TLDR: Can the stock Model 3 seats withstand the loading force applied in an accident when using a bolt in 4 point harness and HANS device?
 

Sam1

Active Member
Sep 11, 2019
1,730
1,824
NV
I can't vouch for the strength of the OEM seats, so this may be a contradictory statement... However, you would never catch me setting up HANS on any factory seat without some type of reinforcement. Multipoint harness, maybe. HANS, no way in hell.
 
Huh, well first of all thanks for replying. Unfortunately I don't think I fully understand what you are saying. You'll have to forgive me as I am very new to Motorsports and its relevant safety equipment, I am still learning a lot and was just aware of the efficacy of HANS and many drivers saying they would go on the track without it.

Are you aware that Schroth Quick Fit Pro is a 4 point harness that allows use of HANS with factory seats.

Schroth has actually tested the seat with this configuration and found it to be safe (not for model 3 but for BMW e90 3 series and other cars).

When you say reinforcement. Are you talking about the mounting of the harness to the car or reinforcement of the seat itself such as using a stronger racing seat? When I called Schroth they strongly gave me the impression that the weak link would not be where iImount the harness to the structure of the car, but rather the strength of the seat back (potential collpase in an accident). They did not think the harness would get ripped out of the mounts.

Thanks for the reply!
 
It seems extremely unlikely that the seat frame strength in a BMW E36/E46/E90 (Schroth makes HANS compatible harnesses for all) would be more than in the Model 3. Personally, I wouldn't worry about that. Myself and others have been using the E90 Quick-Fit Pro with HANS without issues thus far. The only concern would be your height. If you are on the shorter side (5' 6" or less) there will be a notable gap between the shoulder straps and your shoulders based on the height of the seat back. A taller person would not have this concern.
 
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Sam1

Active Member
Sep 11, 2019
1,730
1,824
NV
Huh, well first of all thanks for replying. Unfortunately I don't think I fully understand what you are saying. You'll have to forgive me as I am very new to Motorsports and its relevant safety equipment, I am still learning a lot and was just aware of the efficacy of HANS and many drivers saying they would go on the track without it.

Are you aware that Schroth Quick Fit Pro is a 4 point harness that allows use of HANS with factory seats.

Schroth has actually tested the seat with this configuration and found it to be safe (not for model 3 but for BMW e90 3 series and other cars).

When you say reinforcement. Are you talking about the mounting of the harness to the car or reinforcement of the seat itself such as using a stronger racing seat? When I called Schroth they strongly gave me the impression that the weak link would not be where iImount the harness to the structure of the car, but rather the strength of the seat back (potential collpase in an accident). They did not think the harness would get ripped out of the mounts.

Thanks for the reply!

Sorry, was a bit confusing. I meant that if I was participating in an event where I thought HANS was a necessity (or required by the track/safety), I wouldn't want to worry about some kind of kit attached to the factory seats where the harness may have the potential to slide off the HANS.

That kit may work and sounds like masterc17 has specific experience with this car and that stuff. I'm going off my experience with purpose built circle track cars. My thing about safety equipment is that you only get once chance to put it on, if you need it, it's too late to change your mind & that's why I would just get that bolt in kit from UPP.
 
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Is the Model 3 headrest the reason why the QuickFit Pro isn't approved?
 
Maybe, but the Model 3 has a headrest with movable posts lol
When I was removing the headrest somehow the spring clip popped off completely and I couldn’t get it back on. The service center fixed it for me as Goodwill but I never figured out how they did it.

Also a driving coach for SpeedVentures told me it’s not safe to use a 4pt. Have you caught any flack with all the track days you use? I’m considering the Simpson Hybrid instead now.
 
When I was removing the headrest somehow the spring clip popped off completely and I couldn’t get it back on. The service center fixed it for me as Goodwill but I never figured out how they did it.

Also a driving coach for SpeedVentures told me it’s not safe to use a 4pt. Have you caught any flack with all the track days you use? I’m considering the Simpson Hybrid instead now.
There's a lot of conflicting opinions on safety gear like this. Most people subscribe to either completely stock or full out cage, 6-pt, and fixed backs as the only options; I don't entirely agree with that. Quick-Fit's have been around for decades and I've never heard of anyone faring worse in an accident because of a 4-pt than a 3-pt.

That being said, after moving to a fixed-back seat I don't find the 4-pt harness to be useful anymore as the seat holds me nice and tight it becomes redundant for what I was using it for (keeping me in place).

If I were to do it all-over again, I think that Recaro Sportster's with factory harnesses is the ideal solution. You can add side airbags and heated seats to those if you want, which is pretty sweet. The fixed backs are also pretty uncomfortable.
 

Mash

Active Member
Supporting Member
Nov 10, 2019
1,234
1,074
Prague
There are no doubts that quickfit holds driver better than 3pt belt. 3pt is a measured compromise - anything safer is less comfortable and therefore less people would use it. Absence of anti-submarine belt on 4pt certainly makes it less safe than 6pt, but 3pt have even more problems than 4pt.

I believe that 3pt on a fixed back is the worst case scenario, because usually it prevents bottom belt from properly holding pelvic, so submarine effect is enormous.

And submarine effect is not about slipping off completely under the belt, it's about the fact that if you don't stop pelvic, the rest of the body gets very hard hits.
 
Jumping into an old thread as I'm looking to harness solutions for an M3P. Curious about two things, did the OP end up going with a quickfit pro? Also, how well does the quickfit hold you in place compared to the normal belt?
I agree with @MasterC17, it is a well worth it purchase. Especially if you are on sticky tires, only took me one day on A052's to hit the order button on the quickfit after being pinned to my door around every right hander.
 

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