Bolt placement for a Racing Harness

[adrians]

Looking for some ideas here before I go drilling holes in the rear firewall ! ! !

I want to install a 4 point racing harness in my spider (RHD), for the lower bolts I can use the existing seat belt mounting points/bolts/holes. - For those supersprint days !

However for the upper shoulder belts I'm not sure were to drill the holes in the rear firewall. Is it safe to drill through the area directly behind the drivers seat ( RHD remember ) just above the top of the upper rear seat ?

Any help appreciated ! !

[mdrburchette]

Maybe you should consider installing a rollbar. The upper belts of my 5 point harness are bolted to the rollbar. The back firewall is actually two sheets of metal so you'd have to drill through both and possible reinforce it with plates. Another thing I'd be concerned about is if you were in an accident, what would happen with the seatback with the seatbelts mounted so far away. Maybe I'm being overly cautious and don't understand how fast you go during a run.

[adrians]

Thanks Denise,
I figured the rear wall was only light metal and would need to reinforce it with a plate on each side.
I am looking into a roll bar as well - which could be removed easily since the car is ‘more for show than go most of the time’.
However I am using it again in a SuperSprint event with the Ferrari Club at the begin of March, there won’t be really high speeds only 130/140km on the straight – If I’m luck.

I think it’s time I look at buying another car for these track events if I’m going to get serious ! !

Thanks

PS More track photos

[mdrburchette]

Here's a pic of how mine is set up. Ron added a piece to ensure the seatback wouldn't bend back and under the rollbar in case of an accident. The rollbar is removable.


Here's a pic of my car on the track. Can't wait to try it out with the new suspension!

[mbouse]

maybe someone will correct me, but that rear "firewall" is actually two pieces of sheet metal with approximately 1/2" gap between. Won't the tightening of the bolt collapse that gap?

[mdrburchette]

I noted that in my post too Mike. I don't know how thick the sheet metal back there is or what would happen if there was force laid on the seatbelt but maybe using steel plates on both sides might spread the load a bit.

[baltobernie]

FWIW, the rearmost panel (the one visible from the trunk) is quite sturdy. I welded the %*&$ out of it when attaching an aftermarket battery box to replicate later model Spiders. But I agree that it's not the place to attach a harness.

[mbouse]

it's not the two pieces of sheet metal that bother me as much as attempting to reinforce behind them, and not being able to adjust for that 1/2" gap... that gap concerns me. it will most likely crush in an impact, then tear at the edges of the reinforcement and not provide the strength desired.

[adrians]

Mike, I understand about the gap !
I was considering drilling larger than required bolt holes and slipping a tube spacer between them ( the panels) and the reinforcing plates to ensure I didn't crush the panels together.
So what’s the alternative if I don't have a roll-bar available! Do I mount the harness on the rear floor so that the belts come out between the upper and lower rear seat cushions?
Denise, do you have a photo showing were the roll-bar bolts to the floor?

PS : I taking the car today to be measured up for new Springs - the owner of Fiatorque said he wouldn't sell me springs if he couldn't measure the car suspension parts first and they would be custom made, - they will be the same price as Kings Springs off Ebay.

Thanks all for the help

[So Cal Mark]

adding a roll bar would increase the chassis stiffness substantially, it's worth the effort especially if you're flinging it around a track

[mdrburchette]

Here are some pics of my installation.
In this one, the interior quarter trim had to be removed. Some people modify and reinstall it. I chose to keep them off:


Here's where the back leg bolts inside the wheel well:


Here is where the front leg is attached. In order to gain access to install the nut, I cut a hole in the back seat tray and inner rocker panel. Some people use extra long bolts and go straight through to the underneath of the floor pan. I preferred not to use such long bolts.

[baltobernie]

Does anybody make a three-piece rollbar for the Spider that could easily be detached when not needed? If a regular rollbar was modified by cutting and fitting with a sleeve (to make it removable), would it be disqualified by a tech inspector?

[ga.spyder]

Hey Adrian,
You might send out a private message to Manoa Matt.He has a roll bar for sale,or at least he did as of a couple weeks ago.
Craig

[racydave]

If the sanctioning body of the race track mandates a 6 point harness, they may be concerned how it is installed also...

[manoa matt]

I have/had two roll bars. I sold one and shipped it to Wisconsin. Shipping was $284 via UPS. Someone from Florida emailed me yesterday about the remaining one and I responded with the price and shipping. No response yet. I'll keep you posted when I hear back. Hawaii is just a bit closer to Australia than the Mainland; don't know how much that will affect shipping.

Matt