N80

Getting a custom roll bar in September. I have a hand-me-down Sparco race seat. Now I need a harness. HPDE , maybe TT, no WTW obviously.

I'm probably going to get a 5 point. Will attach shoulder straps to harness bar/roll bar. Will add a mounting point under the seat for the sub strap. Wondering if I can use the OEM seatbelt mounting point for the left side lap belt? If not, will have to drill another hole in the floor for that.

The problem is the right side lap belt mounting point. The OEM mounting point is on the seat itself.

The Planted seat bracket on the race seat has this mounting point built into it just like the OEM seat. I'm guessing this is not an adequate mounting point for the 5 point lap belt.....but not sure why it wouldn't be okay if it is okay for the OEM belt.

Anyway, I probably won't use that point which means I'll have to drill a hole in the transmission tunnel to install a mounting point. Since I have no been under there in a while, my question is whether or not there is room in the transmission tunnel to put a bolt and mounting plate? Also, are there wires or lines there that I need to be careful about? Would be interested in hearing other's experience putting in their mounting points. Thanks in advance.

dkmura

iTrader: (64)

One thing to consider is the mounting of your restraint system is at least as critical as the quality of the seat and harness themselves. I'd suggest you consider a camlock 5-point and study how to wrap the shoulder harness and lap belts properly. In my SCCA Touring Z33 racer, I use the OEM seatbelt mounting points if at all possible. The Planted seatbelt bracket should also work just fine. Wrap the harness using the bolt-in end and rectangular bracket and measure how much slack you need.

One final hint: make sure the mounting angle of the shoulder harness is close to 90 degrees as it goes through the seat holes and over your shoulders. Exceeding this angle has resulted in spinal injuries during a rollover.

guitman32

iTrader: (15)

Its so easy to go 6pt at this point I think you should. Its only one extra hole and mounting plate.

Your orgs will likely pass mounting the right side lap belt to the planted bracket, since the bracket itself does use the OEM mounting points. But ideally speaking it should be floor mounted independent of the seat mounts. Unless you are sure your seat is mounted rock solidly, the harness will keep you and your seat in place should the seat itself or seat mounting points fail.

In this case that would mean either the planted bracket itself or its 4 mounting points have failed (unlikely) for the lap belt to fail, but still redundancy is redundancy.

N80

Thanks guys. The race seat will be in the car when the roll bar/harness bars are measured and fabricated so that should put the harness bar at the right height, which should make the should harness angle correct.

I'll follow all the manufacturer wrapping instructions.

The seat bracket is firmly mounted in the OEM mounting points so if the belt attachment point on it is secure (it should be, Planted makes good stuff as far as I know) it would save me a lot of trouble.

I am looking at cam lock harnesses. Will consider 6 point.

The floor of the Z is two layer. Did you guys use crush sleeves?

dkmura

iTrader: (64)

My seat mount uses the four original seat mount inserts and OEM bolts. My fabricator custom built the mount to utilize these locations and hopefully, Planted did too.

Blurvision

iTrader: (4)

If your going to go all in, might as well do a 6 point. No reason not to.
There is plenty of room on the inside to drill with a nice eye bolt. Backing plates both sides are mandatory.

N80

Yes, the Planted bracket mounts into the OEM seat mount holes so no problems there.

The problem will be the mounting point for the sub belt (or belts, if I go with a six point). If you drill a hole through the floor you are drilling through two layers of metal with space in between them. So even with a backing plate these two layers could compress when you tighten the bolt down. A crush sleeve could prevent that but not sure if it is necessary.

N80

Just one more hole to put in the car, but yes, that's not a big deal.

Not sure what you mean by 'both sides'. Do you mean a backing plate for the left and right lap belt mounting points? Or do you mean a backing plate under the car floor and on top of the floor (inside)?

At this point I'm seriously thinking about using the OEM seat belt mounting point for the left hand lap belt and mounting the right hand belt on the Planted seat mount. The mount is very sturdy, attaches to the 4 OEM seat mount points and would prevent me from having to drill into the transmission tunnel (the strength of which might not be as sturdy as the floor panel anyway).

Blurvision

iTrader: (4)

Your top concern should be the ANGLE of the belts when installed in your seating position. This is the most import safety consideration. The transmission tunnel can easily be reinforced with plates. Yes inside and out. Same with any bolt that passes through the weak sheet metal.

OEM belt location for the left side should put you in the right spot and is beefy.

See the guide, its all spelled out for you. This applies to any brand harness
https://www.schroth.com/en/segments/...tructions.html

Blurvision

iTrader: (4)

Example of my install
https://my350z.com/forum/autocross-r...l#post10340496

terrasmak

iTrader: (8)

I did the standard 4x4 plate on the inside trans tunnel across from the factory mount in the outside. Then also did a 4x4 plate for the sub mount. Mine is only 5 point , will go 6 point later

N80

That's an impressive install. My sub mounting points won't be as fancy but should be sturdy enough.

How hard was it to get the whole speaker box assembly out? I'm assuming it involved cutting? With what?

My installer is going to cut some of it away to get the hoop back far enough because I'm tall. Wondering if I should just remove it altogether?

Does it provide any additional rigidity that would be lost? I guess the new roll bar will account for that?

N80

Thanks. I've been studying that for a while. Its just the 350z specific stuff that I've got to figure out.

N80

Was there room enough to work under there? My B-I-L has a huge industrial lift in his shop. If it can adjust it to fit my undercarriage I might see if I can use it. Would make it so much easier than jack stands in the driveway.

N80

I'm going to bump this question because I'm seriously thinking about moving the speaker box assembly from behind the seats. I saw in Blurvision's link to his build that he used a spot weld reamer. I can get one of those easy enough and I've got a grinder and can borrow a sawzall if needed. So I think I can get that job done.

What I'd really like to know is if this is going to affect chassis flex? Blurvision put in a pretty substantial roll bar system. Mine will just be a 4 point bolt in with a single diagonal. If removing the speaker box will decrease chassis rigidity will a simple 4 point bar make up for it?

dkmura

iTrader: (64)

Yes, it will decrease some lateral stiffness to the Z33 chassis and adding a four point rollbar will not replace it. It'll also cause problems in the future if you elect to go Spec Z or SCCA racing.

N80

Thanks. That was my concern. Not that I'm going to use it in racing. I'd remove it if it helped with the roll bar fabrication process and didn't weaken the car but at this point I'll leave it in place and let the fabricator deal with cutting out some of it to allow room for the hoop.

guitman32

iTrader: (15)

The only real reason to do it is weight savings, and it is low hanging fruit in that regard. Now would be the time to do it.

I thought Spec Z loosened the rules allowing for its removal:

"j) Rear speaker Main Box 74552-CD))), center support bracket 74552-CD000,
center support connecting bracket 74554-CD010, side brackets 766A6-CD000 and
766A7-CD000 may be removed."

https://nasa-assets.s3.amazonaws.com.../2017SpecZ.pdf

N80

For my purposes I'd rather have the strength than the weight savings. I'm not competing in anything at this point. I'm looking for safety more than performance. I think if I was adding an actual cage it would be different since the cage would give added strength and make up for any loss of rigidity. I might do TT at some point and I'd have to dig around in those regs before I made any other mods.

Plus, this is a bolt in roll bar. If I want to remove the speaker box I could do it at any time.

Blurvision

iTrader: (4)

To answer your questions. The speaker box is dead weight. Cut it all out. Grinder spot welder ect, takes an afternoon work. Its super flimsy.

Sounds like your having a custom bar made up, it should provide the most protection possible with the least amount to compromises. The speaker box just gets in the way of your goals.

There is plenty of room in the trans tunnel for the required backing plates, no concern there.