clib

Main point of this post is to give some additional info if you are considering installing the BK shoulder harness mounts. I wanted to put harnesses in for DE days but didn't want to go the whole bolt in rollbar yet. (This is not a thread to debate about rollbars and their safety/utility) just a couple pointers if anyone is considering installing the BK R1046 mounts. I couldn't find much on the 718 and only a couple on the 981 with description but most get a bit sketchy on information regarding reinstalling the carpet, the plastic and metal rail that hold the carpet and finishes things off. This is the stuff I was most concerned with - how much cutting/trimming/destruction was necessary to get a finished looking mount.

What you can see in the pic is the actual BK mounts are substantial in size - I'm sure they need to be for safety.


BK mount with fixed 3-bar harness mount


But the BK mounts do protrude forward, below and above the plane of the horizontal truss. Also the top of the mount will cover some of that recess in the horizontal truss, which is where the plastic piece mounts into (necessitating sawing the mounts away from the plastic piece). BK discusses this and shows a pic of the cut plastic piece. So to get that carpet around the bulky BK mount required more than just a single carpet slit the instructions describe.



The slit is needed to let the mount/harness through. But, You will also need to trim most of the hard foam backing in the area away to make room for the BK mount and allow carpet to reach its original destination. You'll see a large triangle that goes under the truss - I had to remove most of that to make it fit.


I would also add that the actual slit in the carpet - if you are going to reinstall all the pieces, should be about 1.5cm higher than BK instructions - basically at the top of the triangular foam piece.

Second was how to attach the harnesses to the mount that was safest. If I was also going to the trouble to install harness I wanted to be sure I was doing it according to what schroth recommends to avoid slippage. A lot of posts seems to loop the harness around the schroth bracket attached to the BK mount. Basically > run the harness through a small slit in the carpet > loop over the schroth bracket > and then back outside the carpet to a 3-bar strap a variable distance away to secure the harness. I am not an expert and don't know the real world implications, but doing it that way does not seem to be recommended by harness manufacturers. This post here is the most concise description/advice from schroth I could find on ways to safely affix the harness in a recommended manner. Also talks about the various sizes each pairing might stick out from carpet:

https://rennlist.com/forums/gt4/9497...l#post13566350

Ultimately I used the 3-bar fixed mount directly attached to the BK mount as it seemed simplest to install, to check on over time, adjust when needed. You can see this here and how much it sticks out in the final pic where I have things mocked up to test fit. The seat all the way back does not come close to it.




Overall, the BK mount is certainly well made and solid. Just be aware when you see the final pics of it covered that some additional trimming is needed - maybe that is obvious to the rest of you. I still think its the least intrusive option I could find for a harness mount. When removed the only visible will be a small slit, and I can either reattach some suitable foam or replace the pad entirely. Most of the others required drilling or removing fixed welded tabs.

Hopefully helpful to someone considering it.

Bill

TurboCup87

Thanks for the write up! Which harnesses are you using? I haven’t found Schroth ASM harnesses for the 718 GT4 and don’t really know if Schroth makes them.

clib

I am using 6 point GT3 belts so not sure if the asm system specifically available. Thought i had seen links to it.

bswift

Thanks for the write up! Doing the same install this weekend and this is sure to help avoid some headaches.

TurboCup - These ASMs are likely what you're looking for: https://competitionmotorsport.com/sc...rness-anti-sub

TurboCup87

Thanks a bunch! I had checked a number of places and couldn’t find them.... even on Schroth website.

ExMB

Schroth USA

TurboCup87

thanks. I had checked several times last summer and fall on Schroth website. They had never listed one for 718 (still don’t apparently). I wasn’t positive that the upper mount for the 718 was actually the same.

usctrojanGT3

I would have so purchased this for my 718 GT4 but I replaced the carpet and plastic trim on my 981 GT4 so I have the cut carpet and plastic trim for the roll bar to get installed.

ExMB

I'm saving my 981 stuff, plastic - half cage - etc, for the RS.

ExMB

Delete - double post

needmoregarage

Thanks for posting the detail. I am planning to install these BK harness mounts (or rather my dealer will do it for me). I’ll share these details with them to help save some trial/error time.

JP66

Bumping an old thread 'cuz after waiting a year my 2022 Boxster GTS with LWBS is set to arrive next month, and I plan on having Speed Sport Tuning install a Schroth Harness attached to a BK mount.

I'm sure it must be obvious as no one posted pictures, but how are the side belts and crotch belt attached to the car? Does one need to buy other parts?

Thanks in advance to any that can help.

Tom Loder

Thanks for bumping this up to the top. I just took delivery of my GT4 and am also looking at safety solutions.

I like the simplicity of these, but I have a couple concerns with this design, and most of the available bar designs.

I know BK says their product passes crash test criteria, but what about the aluminum chassis bar they attach to? Is that designed for longitudinal stress of a crash?

The conventional wisdom is you don’t want to be in a harness without an actual roll bar that would prevent the roof from collapsing in a rollover event. The harness prevents you from sliding down in the seat to avoid impact.

BBi offers a four point “harness bar” that doesn’t provide rollover protection. Other manufacturers sell 4pt “roll bars” that look very similar to BBi which makes me wonder if they offer any actual protection.

I guess if you are just looking to hold you in the seat, these brackets are good but you are potentially less safe unless you pair with a real roll bar.

Last_935

These are the harnesses I have in my GT4. They are the only DOT-approved harnesses designed specifically for the Porsche LWB seats.

Schroth Porsche 4 Point Harness for Carbon Seats

JP66

Yep. Totally agree with everything you said. Convertibles and harnesses are a much discussed topic in the Racing and DE forum with some folk coming down hard on the side of "I'd never put a harness in without a roll bar" or even more restrictive as in "I'd never track a convertible". Personally, I consider it incremental safety and added support when cornering so you don't slide around quite as much. Without question adding a true roll bar would be even safer, but for me that is absolutely out of the question aesthetically speaking.

EDIT: I poked around on the inter webs to see what data, if any, I could find regarding Porsche Boxster and roll over crashes. The only one I found the guy actually walked away. Guess that's a good sign