I've been reading all the suspension improvments that Trekkor has been doing, the car is getting stiffer/stronger parts on it, but how much more effective would all these parts be if a cage was installed?

has anyone done back to back testing without and then with a cage with no other changes???

mhmmmm, cages ....

need a "smilie" with handcuffs, hahahahaha

I dunno. At what point do you wanna have the front & back ends move semi-in-concert? Just a cage won't accomplish this. Ya gotta add some extra tubes.....mine is in the "semi" catagory cause I need more tubes, but it's a heap (maybe even a shitload)better than stock.

I am thinking cage and chassis stiffening.

I love welding. Are there cage kits that will pass current certification/inspections for th DYI guy?

The point when you "NEED" a cage, is when your car is upside-down, 4' off the ground, at 100mph!

The added rigidity is a fabulous side-effect, but I'm not sure I would install a cage with that in mind as the primary objective.

Here's a related question: Is it safe driving w/o a helmet on the street when you have a cage installed? I suppose a harness should keep your head well away from the bars...

The ideal situation is to NOT drive any caged or gutted (of its soft interior) car on the street.

However if a cage is properly designed, I think the tubes are well enough away from critical body parts that the odds of injury are far reduced. This assumes that you have a good restraint system and seat, too, which the stock parts probably do not fulfill.

Basically I (and a lot of other folks) believe that if you have a cage, you should go all the way with harnesses, seats, steering column/wheel mods, fire safety, and a head & neck restraint... The cost of all this safety eqpt. adds up fast but is an essential investment in my view.

my usual response ...

if you hit something hard enough to really bang your head on the cage, it doesn't really matter because you would have banged your head on the windshield frame or targa bar or somewhere else if you hadn't installed that cage ...

btw. you're supposed to have padding anywhere where you can possibly hit the cage with your head ...

Andy

the SCCA rules don't allow extra bars added to a cage for the pupose of stiffening the chasis. I know that NASA follows the SCCA cage building guidlines as well. If you're planning on racing, buy a rulebook before you build anything. There are companies that make pre-bent, pre-cut cages that you can weld in yourself that are race legal. Cost will be anywhere from $600 to $1000 depending on where you get it and whether or not you want things like nascar style door bars. If you're seriouly considering a cage, check out goto:Racing. We build custom cages from scratch at pretty darn good prices. We just finished an awesome cage in a Honda Del Sol this last weekend which has the same extra rules that apply to 914's tacked onto it.

*edit* Hmm. It would appear that our site's forum, and gallery are having some problems. If you are at all interested, or just have some questions, and things aren't working just gimme an email.......oh...and sorry 'bout the shameless plug.

No shit?
Here's a legal FP SCCA AXer

yep....but if you were to try to run it in an IT class, or say, one of NASA's enduro classes, you'd be classed as 'unlimited' because of your cage.....if you've still got your stock engine, that's bad......course, if the car's fast enough, thats where you want to be anyway.

Mike,

All the cages you have seen (including yours) are all 1 bar away from SCCA ITA legal. They do not provide any rear or front suspension point stiffening. Yes. Some of the "spring" in the cars is being absorbed by chassis flex (this is why the rear shock towers rip away from the body when you start introducing 300# and higher springs into a stock tub with NO bars leading to the shock towers.)

PCA says:

We cannot have bars passing through the rear windows in our production classes.

SCCA says:

If you dont have any bars going back from the main hoop you have to run one going forward (Petty Bar.) You have seen only 3-4 out of the 15-16 T has done with Petty bars because those people needed it for SCCA (Julius/Hole/....)

B

Great question, not because I know how to weld... cause I don't.

But I would like to know the answer to that.

I believe this or the other 914 board had a recent post on roll cages.
When do you get a roll cage. Well, for me, it was following driving the 914 bact from New England and realizing that the Buick's tires were at the height of my head! I went with a weilded in Stable energy cage with side impact bars. I also went with the 3" five point harness. I pad the roll bar adjacent to my head, but I'm not fooling myself, the padding does not replace a helmet in protective value. Most data reveals more leathal injuries occur with ejection. The roll cage and harness when used correctly, restrain movement. Additionally, with this roll cage, I can still attach my targa top. I believe the SCCA rules describes roll cages which tie into your suspension system as criteria for advanced class.
L. McC

we run rear bars as our 7th & 8th mtg points and a petty bar. Vintage rules prevented us from going all the way to the top of the shock towers but we still gained alot of rigidity at the rear with them.

I don't believe the petty bar which we have as well adds any support to the rear (aft of firewall) section. They do complement each other however.

Regarding driving a caged car on the street. Our little cars seem to get even smaller when you start putting all those welded tubes in them. You will have tubing inches from your head compared to the stock interior.

I don't think anyone could say with certainty that you are safer on the street with or without a cage.

dr

In my GCR, the number of tubes are not limited, only the number of attachment points to the body, and that's only in IT (8 attachment points). In production, you can mount to the body as many times as you like and use as many tubes as you like. You can get creative and add a lot of stiffness to the body/chassis with these "restrictions."

So, I don't understand this statement: "the SCCA rules don't allow extra bars added to a cage for the pupose of stiffening the chasis."

I just wish I could use the engine as a stressed member to connect the trailing arm points across the car.

Just trying to clear up the discussion.


Brad, thanks for the tip on the shock towers. I didn't realize this and will move my main hoop supports accordingly. I already put the plates in the rear above the inboard trailing arm mount, but I'll have to put some more in and run a tube to the shock tower.... progressing slowly......

Well said.

I put a full cage in just to be safe, but couldn't believe the handling difference when I first took it out. It was simply a different dimension (literally) as the car wasn't twisting all over the place.

My guess is that a full cage will get you 1 to 1 1/2 seconds on a 50 second AutoX course.

its in the rulebook for IT cages, though i'm really not too sure why. don't have my rulebook with me, so i don't have the exact wording of it, but its there. if you run a production class you don't have to worry about that part.

actually, one of the cool things about the 914 (and the previously mentioned del sol from my earlier post) is that because you don't have to have rear stantions, you're required to attach the main hoop to the seatbelt mounting points, which is against the rules for other cars. and you don't have to remove that attachment if you add the rear stantions. the two together actually add a lot of stiffness to the chasis.

From GCR, ITCS, page 23, Section 10.a.1.A.5. "Any number of tubes may attach to the plate or each other which shall be considered one point."

Page 24, Section 10.a.5, "...Any number of additional reiforcing bars are permitted within the structure of the cage, provided they meet the minimum tubing size...."

Page 24, Section 10.a.4, "Main hoop braces may be mounted at the rear shock mounts/towers or the suspension pickup points...."

You may be thinking of the section that prevents one from penetrating the firewall... page 24, Section 10.a.4, "...No braces may pass through the front firewall." which could lead one to that conclusion.



I decided to turn my 914 into a race car once I realized what the Detroit roads were doing to the body/chassis. The potholes were flexing the body so much, I figure the only way to save the car was to through a cage in it and go racing.

Yeah.....kinda......basically the IT rules restirct where and how many places the cage can attach to the chasis, which limits how much your cage can stiffen it. hence the big advantage of being able to use the seatbelt mounting points. didn't quite manage to explain what i meant as well as i would have liked earlier.......its easy to know exactly what i'm talking about when i'm the one talking.....not so easy for other people to read my mind, it think. oh well......

Cool. I understand what you're saying.

My point is those 8 points can be located to stiffen the crap out of the body.... with the exception of the front strut towers.

The previous cage we installed in our ITB VW GTi was prepared within the rules. The cage really stiffened that body up, no question. But, since it was IT, I couldn't tie in the front strut towers (couldn't penetrate the forward firewall). With my previous ITC Scirocco, the strut towers started to pull away from in the front inner fenders after many very rough years of faithful service. So, eventually this could develop into a problem on that vehicle. More weight on the front wheels, and high spring rates, and little travel.... now I'm running P-car.

My current cage (production car in process) has many attachments to the body. The main hoop is welded to the targa bar in many places, even the harness bar is welded to the rear firewall. This freedom in production vs. IT is nice, but you can make an IT car very stiff, too.

Another interesting thing in IT is that you can use 100 square inches of plate on each mounting point. Used intelligently, that alone can stiffen up a body.

That's one thing that really upsets me about the bolt in cages. The plates they use are usually only single plane and painfully small.

There's a shop in Scotts Valley that can do 914 rollbar for PCA and POC TT's? Where is it located? I would much rather keep my car local as my wife has an office on Scotts Valley drive.

on south navarra dr. we're working out of our garage for the time being.

Damn...100sq.in. for each mounting plate?

Milpitas isn't too far away

TC Design

Tony did my cage as well as quite a few others here .....he's good, otherwise I don't think he'd be working on as many GT2's and GT3's as he does.

yep. tony's good. he also charges about 3 times what we do, sometimes more. we can also get your car on a saturday morning and have a full cage in it by sunday evening (assuming the interior is already out), since we don't have cars lined up around the block yet. hopefully one day, we'll have as a good a rep as that. we do good work, and it keeps getting better.

I know Tony at TC Design does great work he did all my suspension work. He does an excellent job. He is looking into a potential roll cage with bolt on extension that will qualify for PCA and POC events. I need a couple more inches to clear my helmet. I still like the idea of somone who can work on the car close to where my wife works. Makes it a lot easier for me to drop the car etc.

There are several reasons why I charge more than you, I highly doubt three times though.

1) I have a real overhead, I don't work out of a garage.
2)Look at the quality of the fit, welding, and real engineering behind my cage designs.
3) I have an extremely large insurance policy, look at some of the cars that come into the shop, GT2's and Ruf r-turbos.
4) I am still cheeper than other shops doing the same quality of work I do, McGee, Racer's Group, Rolf, ect.

I don't mean to disrespect you, but you get what you pay for. And in this case we are talking about cages that could potentially save your life. I have built 57 cages THIS YEAR and have three cars in the shop currenty getting cages.

btw: your hourly rate is the same as mine according to your website.
-tony

Tony's prices are more than fair for the quality of work he does. Based on rough quotes to me his fabrication prices are very competitive.

...And there is a good chance I will likely haul my car over the hill for him to do my work in the future.

tony,

just saw your site for the first time. Awsome display of 914 fabrication. I'll have to study some of the cages later when I have more time. Saw a few things I would have liked to do on my cage. (not sure if it is legal for our class though)

nice work,
dr

i don't want to give the impression that i'm dissin' your work. i've had the chance to see a couple of your cages in person and they're awesome. in fact, we've learned loads by looking at them, and wouldn't hesitate to recommend you as a cage builder. just trying to get out there as a cheaper but not shoddy alternative.

I thought I'd use this thread to ask for some help. We are going to connect my cage to the rear shock towers in the very near future. If anyone could post pics on what others have done I'd appreciate it. I'm questioning whether I just need to attach a tube to the front of the tower or if a plate should be fabbed to the top of the shock mount itself?

check my team website at:

http://www.synthesisdv.com/vg/vg%20complete.html

lower right pic shows how we did it. bent bars let us operate motor lid. Rules would not let us go to the tops of the shock towers but sides were ok.

TC design has some great pics of rear cage tubes. He triangulates back and then runs another tube forward and down low.

dr

Thanks, that helps alot.

FWIW my only "regret" about my TC Design cage, is that later (mine is a 2002 design) Tony improved his 914 cage design further and became an even better welder. Great work in my experience!

I am also thinking about doing the bulkhead bracing as I can afford the POC points, but I am not sure if it would be legal for VARA or HSR.

For SCCA and most other sanctioning bodies you are NOT allowed to have any bends in the rear down bars.

You can check out what I did with Scott Yeaman's car here:

Scott's cage

-Tony

I remember dealing with the bent tube issue.

In the 2004 GCR, section 11.1.a.4 talks about the rear support tubes. They specify an angle no less than 30deg and the mounting not to be more than 6" below the rear hoop.

I don't see a line regarding bends exept where it says the bends must be gentle angles with no crimping or distortion, min radius is 3 times the tube dia.

I am refering to the production car rules in particular.

dr

You've just touched upon one of the things that pisses me off about the organization of the GCR.......

Check out the section called BASIC DESIGN CONSIDERATIONS (18.1). There's a lot of stuff in that section that people forget about.

For this discussion, in section 18.1.6.C, it says, "....Rear hoop supports: No bends"

But, a buddy of mine just got his first tech inspection on his Miata with bent rear hoop supports and didn't get flagged on it.

I think that the rear tubes are optional anyway on cars with our layout. Many I have seen do not run any rear bars. I have not had a problem with SCCA scrutineer or yearly tech yet.

Guess I could hack them out if I had to.

dr

There are some other rules in that section that apply to all cars that aren't well known.

For example: Main hoop: 4 bends maximum, totaling 180 degrees, +- 10 degrees and Front hoop: 4 bends maximum, or front downtubes, 2 bends maximum.

There is a "get out of jail" card that says you can use tubing the next size up if you don't meet the requirements.

I think there are some scrutineers that don't know this section well enough.

BTW... if you're talking production, those tubes are not optional.

When does a car need a roll cage?

When it leaves the showroom!

If you want the maximum in suspension accuracy then the chassis needs to be built with the maximum stiffness.

We did a car awhile back that used 1 3/4 .095 instead of 1.5 figuring the trade off in stiffness would be worth the wieght. I really don't think is was. The problem with most cages available for the 914 on the market, (Autopower, Etc) don't address the stiffening issue they just add a measure of safety. A good cage should incorporate the whole suspension, chassis and body. Tubes in the right place can make a difference, where just adding a bunch of tubes can just add wieght. I would love to run a scale model of the 914 chassis through an FEA program but I don't know How to get the measurements without a CMM.

Just installed the interior longs chassis stiffening plates today.

I can already feel the differance. But I haven't really *tested* it yet.