HKS7fanatic

hey guys, i already searched to find out the best way to mount a 4-point harness. the M2 harness bar seems to be the best but very hard to find. from what i've read in past posts rotary extreme uses the stock brackets. i checked their site recently and was wondering if anyone knows if the design is changed. thanks for all the help

Sled Driver

iTrader: (9)

M2 "did" make the nicest bar (NLA)

Rotary Extreen uses the stock bar brackets & is a soild aluminum bar (Not hollow steel like M2)

There has been threads that debated it's merits.

https://www.rx7club.com/showthread.p...ar+harness+bar

The web site photo shows the old M2 bar (last time I looked)

7racer

you know that the orginal fabricator for the M2 stuff is re-starting and making the products again. You might want to drop him a pm to see if he can make the harness bar. His name is raceshop.

HKS7fanatic

awesome, i'll have to hit him up then. thanks guys

DamonB

There is no debate. The RE harness bar which uses the stock strut tower brackets is completely unsafe when used as a shoulder harness attachment. Show the strut tower brackets to any safety official and ask if it's safe to mount a harness too. They're either going to think you're joking and laugh, or their going to turn white with fear.

That solid aluminum bar makes no difference at all because its mounting points to the car are useless. Your stock seatbelts are much safer than that.

Section8

iTrader: (6)

This is why I opted to just get a bolt in 4 pt bar to mount my harnesses to. No way in hell i'd trust my life to the strut tower brackets.

HAI-TEK7

iTrader: (31)

^^^^^exactly!!

Thats what i did, and it stiffens the chassis pretty nicely

cmartinp28

just use the stock seatbelt mounts on the floor since you're going to remove the seatbelts anyways

rynberg

1. Why remove the stock seat belts? Are you going to buckle into a 5-point harness just to go take a drive on the street?

2. Using the stock belt floor mounts is great for the LAP belts, but it doesn't answer the question of what to do with the SHOULDER belts.

You either bolt the shoulder harnesses to a roll bar piece, the Raceshop shock tower brace (fabricator for M2 - Larry will be selling these again), or the hatch floor with suitable mounting.

cmartinp28

you dont have to remove the stock seatbelts to mount them on the seatbelt mounting screws, when i removed them, they were about 1.5"-2" long so if you realy want, you can mount the lap and shoulder on them. i would highly recommend mounting your seatbelts there, rather than the hatch floor, only because i drilled through the hatch floor and the sheetmetal seems to be very thin. and the holes for the seatbelt mounts are reinforced and go all the way through the car, you can actually see how thick the metal where it goes through. if the screws are too short for your liking, they are easily replaced by longer ones from any autoparts store

well.. since the shoulder harnesses usually go in the hole on the seats behind your neck, it seems to stay pretty well in the shoulder area.... and mounting them on a harness bar, would pretty much do the same thing as far as positioning goes.

if you have 5 point belts... you can always disengage the 5th point in your crotch area. tell you the truth, i found it uncomfortable sittin on the harnesses in my car, so i just got rid of the stock belt cuz of it.. i found myself just using the 4 point for daily driving, and the 5th point is tucked under the seat

cmartinp28

DO NOT JUST DRILL A HOLE ON THE FLOOR OF YOUR CAR FOR YOUR SEATBELTS!!!
most places that you will drill in are less than 1/8 inch of steel, in an impact, the bolt will rip right off.

if you do decide to drill holes in the chassis, make sure you use backing plates of thick steel to reinforce the hole

DamonB

THIS IS NOT HOW YOU MOUNT A SHOULDER HARNESS! The shoulder harness cannot be anchored to the same place the lap belts are because then it will compress your spine as you are pulled forward in a collision. A shoulder harness is mounted behind the drivers shoulders, not under his butt. You NEVER run the shoulder belts up over the driver's shoulder and then right back down to the floor. You should aim to keep the shoulder belts nearly horizontal after they pass over the driver's shoulders.

G-Force says the shoulder harness should extend from the driver's shoulders at no more than 30 degrees above horizontal or 5 degrees below horizontal. Simpson likes to see even less. This is to prevent stressing the driver's spine!!!

www.gforce.com/pdf/harnessinstall.pdf

DamonB

https://www.rx7club.com/suspension-wheels-tires-brakes-20/questions-harness-installation-443075/

cmartinp28

would it matter that i have the shoulder harnesses mouned on the floor and looped around my roll cage?

DamonB

If you have a roll cage why haven't you mounted the harness to IT instead of incorrectly to the floor?

The shoulder harness should extend back from the shoulders nearly horizontal and then end at a solid anchor point, not change direction and loop around some bar, pulley or any other thing. Doing it that way takes more effort to install and will require the harness to constantly chafe against the rollbar. Not good.

Ask yourself why all the harness manufacturers have guidelines on how to install them correctly. Anything done poorly is unsafe and unfortunately harnesses are all too often installed poorly for no reason other than the owner didn't care to do it right.

SPOautos

It may not matter so much in our situation. If you go thru the hole in the back of the seat then the belts are actually going to come off your shoulders straight and not really wrap your shoulders. They wouldnt actually make a turn untill they get behind the seat. I dont really know if that makes a difference or not...but something to think about. Might try calling the manuf and just asking if its ok to come straight off the shoulder THEN turn down once its behind the seat.

Stephen

cmartinp28

i didnt mount it on the roll cage because i feel that the holes that i might be drilling on them might compromise the rigidity of the cage. second of all.... if the seatbelt holes from stock pass US safety standards, then they are strong enough to hold me in place incase of an accident.

you were arguing the position of the seatbelts, and there are two points in the seatbelt's path that keeps it at the proper angle, the roll cage and the back of the seat. i dont see anything wrong with the belts "chafing" or rubbing agaisnt the roll bar, in actuality the the material of your seat is more abrasive to the seatbelt fabric than the smooth surface of the roll cage

rynberg

Drilling mounting holes for the eye-bolts will not reduce the rigidity of the cage, especially since they should be placed in a harness bar loop, and not the main hoop. In any case, since SCCA and NASA require a drilled hole in the cage to verify cage thickness, I doubt it has much of an impact.

Your thoughts about harness mounting might seem to make sense at first glance but there is no racing organization that would approve your mounting. That tells me it's not safe.

Julian

iTrader: (14)

yes but they are not designed for the combined pull of lap belts plus uppull of mis-directed shoulder belts. The shoulder belts can also be mounted to the roll cage/bar by looping around bar, without using eyebolts. For the lap belts I use eye bolts from harness manufacture, use them to bolt in factory belts and clip on 5 pt lap belts

cmartinp28

julian.... i want to try your suggestion, but how do i go about locking the straps?

Alpine

this WRC car choose to mount the shoulder belt in between the strut tower, rather than directly behind the seat on the roll cage.

Julian

iTrader: (14)

Typical bar would have "U" hoops welded on, should be able to fine a number of photos on web. Kirk told me to weld then on after seat harness alignment. I never did as the belts are held sideways by other fittings, i.e. seat back brace, exh. mount .. also I work out that even if strap moved to end of bar and thus forward around curved part toward main hoop, distance to seat did not change

Julian

iTrader: (14)

My first gen car the belts go back to rear deck (seems deck is higher relative to seat than 3rd gen), bolted through with backing plates

DamonB

Apparently everybody missed this earlier. You're free to mount them however the hell you like, but if you're not following the guidelines you are fooling yourself.

DamonB

If you know nothing about mounting harnesses then why do you insist on doing it along with trying to rationalize how your install is acceptable? It is not acceptable if you want the harnesses to function properly!

You don't have to drill holes through the tubes. You wrap the harness around the tubes with retaining clips made for the purpose. This does not compromise the cage structure.


Ignorance of facts does not make them any less true. Find any harness manufacturer who recommends installing them as you have done. If you have a cage as you insist (and assuming the crossbar is at the proper height) all you have to do is wrap the shoulder belts around the cage.

That's a ridiculous assumption. If the stock belts and mouting points are sufficient why are you bothering with a harness install? Besides, it's not if the mounting points are solid enough. It's the load path through the harness and the driver's body we are concerned about. THAT is what determines how the harness is mounted and THAT is why all the harness manufacturers instruct you to mount them in the fashion I have described!

If you just need it to look cool there is no sense in arguing.