Nice rollbars. One question...is there a structural reason why you didn't mount the xbrace to the stock rear strut brace?

The fabricator for my rollbar is intending on mounting the rear diagonals to the rear strut brace. He's using 4130 Chromoly 1.5" per SCCA rules.

Thanks.

 

Mitch Piper contacted Nismo and had a discussion on the optimum structural rigidity for the placement of the x-brace. It was determined that mounting them to the back of the rails behind the fuel cell provided the best support. That's what I was told at least...

 

Very interesting...I also looked at the Z rallycar and its diagonals were at the strut brace but I would imagine Nismo knows what they're talking about.

Is there sufficient clearance to take out your jack/tools and spare tire? Looks like there is. Was the rollbar somehow pre-fabricated? Cuz it looks like it was painted or powdercoated...nice finish (mine will be raw 4130 chromoly, luckily it's dark).

I will post pics of my rollbar also when it's complete later this week. My friend's fabrication shop (mostly NHRA work) is doing diagonals to the rear strut brace, main hoop, horizontal harness bar, a diagonal from the back of my seat to the front footwell of the passenger seat (connected by a clevis for easy removal should I have a passenger) and any other piping he deems necessary. He's also doing some lateral subframe connectors where the foam stiffening is.

Have you tracked the car yet? Do you think there are any tangible additional chassis stiffening benefits that were noticeable?

Sorry for the inquisition...I'm very curious.

 

I've put at least six track days in since installing it, and I can't say I see any difference. The Z is pretty damn stiff already. And of course mine doesn't have the full X brace that John's does.

 

I'd say there's a minute difference in stiffness, but nothing major. As James mentioned, the chassis is already quite rigid. Not exactly sure how they did the painting, but it's nothing special, just a black Krylon, which makes it easier to touch up. Look forward to your photos.

 

John,
If you look at the Nismo Japan 350ZGT car, all mounting points for the cage, in the rear are at the upper shock/body reinforcement, it has a seperate x-brace that attaches in the space underneath the shock/body reinforcement, this x, attaches to the lower frame rail at the bottom and the bottom of the shock/body reinforcement at the top. All the cages I have seen built in racecars, up to now, have the down-tubes from the main hoop tied into the upper shock/body reinforcement. This is where we have attached the down tubes on the cage in my car. The metal in the corners is double walled and is a good point to weld a mounting point. Mounting the down tubes to the frame rail behind the gas tank is a safe place to mount your rollbar, but since this point is already very stiff you are not adding a lot to the torsional rigidity there, since the upper shock/body reinforcement is not a true "frame rail" you can acutally add torsional rigidity to the car by mounting the cage to this point. When my cage is done I will post some pictures of it

Alex

 

I stopped by my friend's fabrication shop. He measured wall thicknesses at the strut brace and the area that John has his mounted...they are the same. He understands why John's diagonals are placed there...they are right above the springs of the suspension which is typically a place you would want in terms of vehicle dynamics relative to chassis rigidity. My friend's shop is going to do both...at the strut brace and the rear chassis (he thinks it would be more trick than anything else with perhaps some additional benefits).

 

Piper still making these? $900 installed? Will they make slight changes, like moving the vertical bar over the sub-woofer location ILO of the glove box? They are only 6 hours away, and that looks dam tempting

Thanx
Bryan

 

I doubt it's the same price as steel has been creeping in price over the past few years. Doesn't hurt to contact them to see what they'd say though...

 

Everything has been creeping up, will contact when I'm ready to jump

Thanx
Bryan

 

Bryan... I'm not trying to dis Piper or anything... but we've got a couple track event sponsors that do roll bar fabrication that are more than a few hours closer to you

-Stacy

 

Cool, we can talk about it the 21st. After all that what sponsors are for. Thanx

 

Is it legal for road racing to do the diagonal bar inside the hoop like that at two different angles? I didn't think that was allowed?

 

Technically this is illegal for SCCA. I do like this design though since it does not limit seat travel that much. I actually showed my builder this picture when I had mine built and he wouldn't do it like this because he said the split diagonal introduces a weak point. My diagonal is straight but my roll hoop is about 3" further back in the car so I don't really loose that much passenger seat travel. My only complaint is that since I am tall, the top of my rollbar limits my view a little. Nothing a race seat sitting 1" lower wouldn't fix
I'll try to dig up a pic.

 

I gotta get Piper to finish my half cage to a full cage on my BMW.. +1 for the good work and they can make cages to spec.