Roll cages? Really necessary?

[majik16106]

I see a lot of guys on here running decent power through motors without roll cages, most guys say its absolutely necessary for a car getting any track time, but some of the weekend racers seem to not be using them without any trouble.. so it seems to me a cage is good idea, but its not really needed. If you could post up and let me know what your running and if you have a cage and if your having any huge problems...

[Guest Nic-Rebel450CA]

... so it seems to me a cage is good idea, but its not really needed....

 

From my school-of-thought, so to speak, it's the torque numbers that really dictate what kind of structural enhancements need to be done.

 

Here is the ballpark as it has been explained to me:

Under 200 lb/ft of torque... Pretty much anything stock is ok

Over 250 lb/ft, definitely consider subframe connectors.

Over 350 lb/ft, consider small cage

Over 500 lb/ft, consider any possible enhancement

More? Consider salt and/or mustard to go with the prezel that will be left of your car

 

As for myself? I plan to go with a roll cage more-so for safety than for structural strength.

[TimZ]

We had a discussion along these lines not too long ago:

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=22665

 

No conclusions, but a pretty good discussion.

[Pop N Wood]

I have read posts concerning cages with great interest. I am of the opinion that cages really aren't necessary for everyone.

 

Check out this thread

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=22979

 

Another summary thread

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=7409

 

 

So for a street car I feel it depends on whether the car is a 280 or 240. 240's need some type of bracing, but I am hoping subframe connectors will be sufficient. It would be nice to add some type of door bracing since the doors on a 240 offer zero crash protection.

 

For a street 280, well then maybe nothing.

 

Of course if you just like the look of a cage.....

 

A cage on a street car will add a certain degree of safety, but you shouldn't be driving a car on the street in such a way that you actually need one.

 

For a track car, then yeah, I say build a cage if not for safety, then to stiffen the chassis. This will allow you to run stiffer springs than you otherwise could with a stock, flexy chassis. It also gives you a spot to connect a 5 point harness. Also many tracks have a cage requirement for cars that run under a certain ET. So figure out what type of racing you want to do, then build something that is within the rules.

 

The "rules" will impact your cage design. Katman one circulated an ariticle describing ITS spec cages for a Z. Those rules specifically limited the number of chassis attachment points and prohibited extending the cage through the firewall. I got the impression they wanted the cage for driver safety, but added the limits to avoid having the cage significantly stiffen the chassis thereby changing the character of the car. Just a WAG on my part.

[Mikelly]

There are a few things to consider:

 

The Zcar is a pretty GOOD chassis for stock configuration. It is only when you had stiffer springs & bushings, larger swaybars, Stickier & wider tires & wheels, and adjusted suspension settings that you run into problems. Look at a Zcar that has been autocrossed extensively with the above mods. You will notice cracks in the paint at the top of the A-pillar, and back by the rear hatch above the rear side windows and vent. This gives you an idea of just HOW MUCH chassis flex a Zcar gets.

 

In 1993 I had a 260Z that was straight as an arrow with NO rust in the car. We did a full rebuild of the suspension to race it in SCCA Solo2 and by that winter the car showed signes of stress in the above locations. This was with a mild L6 motor, cam'ed, and a header, running a 4-Barrel carb setup and with the ussual ignition mods. The car was no high HP king. That fall I had subframe connectors installed and we did a paint job on it, filling in the seem cracks with bondo and blending it all in so you couldn't see the imperfections.

 

THAT car was totalled in 1996, and by then I had also added a 6 point cage. The car was a regional champion car in the VMSC car club and had MANY autocrosses over a three year spread on it, plus a couple of summit point driving schools, as well as a trip to Road Atlanta with Car guys. You couldn't see the seems, or the locations where bondo had been applied to cover the cracks. The car had been hit from behind and forced into another vehicle and the crash was devestating to the unitbody at the front and rear. However, the "WHOLE" of the car, behind the front struts and in front of the rear struts was in tact.

 

I cut the bolt in cage out of that car and had it X-rayed before installing it in my White V8Zcar. It was perfect, with no signes of stress.

 

I'm now a HUGE fan of Sub-frames and a cage in ANY Zcar because of the reasons above. I think the added strength really helps the chassis regardless of the powerplant. The forces applied to the chassis from the suspension mods really can impact the whole of the car.

 

Mike

[Guest Nic-Rebel450CA]

A cage on a street car will add a certain degree of safety' date=' but you shouldn't be driving a car on the street in such a way that you actually need one.

[/quote']

 

I don't know about you all, but it's not how I'm driving that I am worried about, it's the SUV owners and such that take the "Sport" part of their name a little too heavily.

[majik16106]

The stress from the power isnt what im really worried about. Power doesnt really stress a chassis at all unless your making a lot of torque and running slicks with hard launches, a car see's a lot more stress when pushed through turns as it holds on. Im thinkin since mine is mainly a street car, which will see occasional auto-x's and road courses (and even then wont really be pushed to the limit seeing as i dont want to bust it up too bad) i'll probably run a small 4 point with a big cross in the back, and sub fram connectors, the car has a little rust(nowhere really important) but it is straight. I would like to keep getting input however cuz it seems like people are interested. I started a small debate over this a while ago, i just knwo that there are ALOT of v8 cars running around without cages daily. Im sure the small cage will be more than enough for me.

[Mikelly]

In motorcycling we have a saying... Dress for the crash... In automotive "Sports Car" driving I liken a decent cage and safety belts to the same intent... None of us PLAN to be involved n a crash. The day my 74Z was rear-ended in January 1996, I was in rush hour traffic in side Washington DC's Beltway, and the 6000+# plumbing supply truck that hit me had no intention of doing so... Fortunately my car was "Dressed for the crash"! I had to cut the car in two places to reduce loading on the chassis, and the cage was loaded to a point that is was twisted. When we cut the car in the rocker panel on the drivers side the whole car phyically sprung outward at both ends several inches... That was how much the metal had been compressed from the impact... Yet the cage held.

 

It boils down to what you want to do and what you "Think" is warranted for a Zcar, which is a MUCH SMALLER car when you are sitting in it. My personal preference is to have one, but then again, I've seen how poorly they do in accidents first hand!

 

Goodluck!

Mike

[johnc]

I would not drive or ride on a road race track in any vehicle built prior to 1985 UNLESS it had at least a roll bar, a FIA approved race seat, and a current 5 point racing harness. As an instructor I've refused to teach students who had vehicles that didn't met the above criteria. If they don't care for their own lives I certainly can't expect them to care for mine as I'm riding in the passenger seat.

 

Just like riding a motorcycle on the street, on a racetrack the question is not if you're going to crash, but when.

[JMortensen]

Two quick stories:

 

One, a friend in a '71 was at an auto-x, right in the middle of his run the car felt "weird". At the end of the run he figured out that the drivers side A pillar had detached itself from the cowl. Completely detached.

 

Two, took my ex-boss for a ride around Streets of Willow in my car a (he's been racing Porsches for 25 years, there's even a picture of his hand in How to Make Your Car Handle). He said, you might want to listen for popping noises. I betcha this thing is going to start tearing out the spot welds.

 

I've never found a spot weld that's broken, but I still think about that every time I put slicks on my car.

 

Jon

[majik16106]

well, my car has the 5 point harnesses and the seats sitting next to it, the only issue im personally having is how intricate i want MINE to me, mostly i started the thread just for thoughts. I know with the frequency i travel through metropolitan atlanta (75, 85, 285, and 400) and with how crazy Atlanta's drivers are.. a cage for me is a must if ONLY for safety, my issue was for the necessity of it in a "safe controlled" enviroment without other drivers, my question was aimed more at its necessity to keep the car straight.

[BRAD D]

You need one if you go faster than 11.99 in the 1/4 right??

[Mudge]

I don't know about you all, but it's not how I'm driving that I am worried about, it's the SUV owners and such that take the "Sport" part of their name a little too heavily.

 

I believe what he may be eluding too, is not killing yourself by headbutting your own bars without a helmet.

[majik16106]

You need one if you go faster than 11.99 in the 1/4 right??

 

yah, i think thats the NHRA rule, which my car will definatly break. But like i said, my post wasnt started with the intention of "do i need for legal or safety purposes" but aimed more at a cages ability to stop the frame from twisting up.

[BLKMGK]

It was a simple decision for me - full cage fuly padded. I came to this decision after parting out another 240Z. You see I gutted the doors comepletely and upon looking inside was SHOCKED to see how little they had for support. IF I were ever T-boned in the door I would expect the cage to have ZERO resistance - there's simply nothing in there. The rocker might help but it's awful low to the ground and most of today's cars would ride over it.

 

So, a cage was installed to protect me as best it can. I can certainly try to watch my actions and be safe but I cannot say the same for others. Hell right now every single car I own has a rollbar of some sort in it - even my daily driver Supra. Done right it's not too intrusive, my Z's cage is a bit of a PITA though and I took those lessons learned and applied them to the Supra 8)

[260DET]

On cracking the rear hatch pillars, way back when I originally built the car two supports were welded into the body so as to support the rear roof arch, the part where the interior light is located. They go straight down (viewed from the side) from there to the hatch floor at an angle (viewed from the rear).

 

With the present 300 springs at the rear the body actually creaks when driving over a low kerb diagonally so the body is far from rigid torsionally. Yet the pillars show no sign of cracking.

[Pop N Wood]

It was a simple decision for me - full cage fuly padded. I came to this decision after parting out another 240Z. You see I gutted the doors comepletely and upon looking inside was SHOCKED to see how little they had for support.

 

I read an article that stated structurally speaking the only function a door has on a 240 is to hold up the paint.

 

Trouble is, most cages I have seen offer little additional protection to a side impact. Like stated above, the rocker panel on a Z is below the bumper on most cars/SUV's. A 4 point will only deflect a lucky hit since they don't go forward of the B pillar. Other cages just anchor the hoops to the sheet metal at the bottom without running a bar side to side across the bottom. The diagonals most people put in the main hoop is good to protect the drivers head in a roll over, but since they usually go top to bottom from port to starboard, they won't help support the bottom of the main hoop from a side impact on the drivers side.

 

But the biggest worry is the lack of door bars. And cages that do have them offen have removable door bars. This means they are not as strong as they could be and, more than likely, won't be in place on the street.

 

So IMO you are not buying much additional side impact protection unless you plan to gut the doors and build a NASCAR style set of door guards that project into the door cavity. And a cage like that would be highly impractical on the street.

 

So having said all that, the important thing to keep in mind is you are playing probablities. Like stated above, a crash in a race car is not a question of if but when. The more serious the racing, the greater the need for additional structural safety.

 

But for a street car, it is simply not clear to me that a cage is "necessary". I don't think a Z, even an early one, is any less safe than say a convertible Miata. If I were truly that worried about it, I would be driving a Volvo instead of a Z.

 

Two last things. I think torque stress for a V8 Z is something to worry about. I have read postings from people who have had trouble shutting their hood after a couple of spirited drives in a V8 Z. Since many of us are driving around on 30 year old chassis's, some type of reinforcement only makes sense. The thread on 240's vs. 280's is food for thought.

 

Second, not all cages are created equal. If you read some of Katman's old posts most cages are just excess weight that only raise the car's center of gravity. Other people have raised questions about destroying crumple zones and the risk of a cage playing bumper pool with your head. There have even been recent newspaper articles stating that government crash testing methods have made vehicles more dangerous because manufacturers have started designing vehicles to do well in the tests while mortality rates have increased. A very complicated issue.

[Mudge]

It was a simple decision for me - full cage fuly padded.

 

Quality padding at that, there is crappy stuff and good stuff, and I dont even know how much the good stuff will help you if you headbutt it at 20 MPH+ collision.

[Tim240z]

It was a simple decision for me - full cage fuly padded.

 

Quality padding at that' date=' there is crappy stuff and good stuff, and I dont even know how much the good stuff will help you if you headbutt it at 20 MPH+ collision.[/quote']

 

That's why they make seat belts/harnesses

 

Tim

[JMortensen]

One thing that always made me wonder: Why do people put the diagonal from the hoop to the passenger floorboard in? I always referred to it as the "head trauma" bar. Is there all that much to be gained over a 6 point cage?

 

I've seen them in otherwise well built cars with no padding being driven on the street! At one auto-x I snap spun and did a 360. When the car stopped I smacked my head on the roof right next to the door hard enough to ring my bell with a helmet on. I gotta wonder what would happen in a similar situation on the street with no helmet going the other way.

 

I think the "head trauma" bar might live up to its name.

 

Jon