1FastRedSC

Looking to strengthen the inner chassis of my 1983 911 sc. If i drive aggressive on the street and occasionally mess around on the track/auto-x, what setup should i go with, cage or bar. And does anyone have suggestions on brands? I've heard of safety devices and autopower, that's about it. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />

M758

Well a good well designed weld in cage will improve the chassis stiffness.

However it sounds like you will see only street duty with occasional track time.

So in my mind the best solution is a bolt in roll bar. Only problem is that I believe the stiffening will be minimal.

The reason I prefer the roll bar is less weight and more space to get in or out of the car. A good cage will take up a lot of space in side or at least appear to. True that the best ones really minimize this, but they still take up space in your lines of sight.

Also there is a risk of banging an un-helmeted head against the side or forward bars of the cage even in a simple incident on the street. The foam padding only does so much!

The roll bar is rather un-obrusive and provides roll over protection as well as mounting points for proper 5 or 6 point harnesses.

Honestly I would not expect chassis flex to be so great that you feel it on the street. True on a race track where every 0.1 sec is important, but street driving is just for fun so I am not certain that it would worth the cost or trade offs required for a weld in cage.

RSAErick

I would imagine that any improvements in handling due to chassis stiffening would be more than negated by the considerable weight of a roll bar or (especially) a roll cage.

Have you considered a harness bar? It probably adds as much or more chassis stiffness than a bolt in roll bar or cage, and weighs considerably less.

Erick

Jim Michaels

I agree completely with M758. I don't know about the other roll bars, but I have an Autopower bolt-in for my mostly street car. It has four feet with bolt plates (four bolts each). Initial Installation might require the removal of both seats (can get by with removing just one seat after the initial install), and some cutting of carpet on the fender wells (be neat, and replace using double-sided carpet tape). You won't have the full range of seat movement afterward (at least for the seat back), and forget about asking someone to sit back there. You may also have to hire a monkey to clean the rear window inside. My monkey does a crappy job. In short, think through all the constraints a roll bar will provide.

1FastRedSC

Well, the 911 is purely fun, and comfort isn't a problem because i am still young and have the ability to adjust and flex if necessary for the improvements to work. And what's a harness bar, does it provide the same structural support as a roll bar?
And by the way, the rear seats are never used anyway.

RSAErick

A harness bar is simply a bar that bolts across the center of the car to the same pillars that your seat belt mounts to - directly behind the seats. It's used primarily for harness mounting, but can function like a strut brace across the center of your car.

A930Rocket

I have a Safety Devices cage in my '87 930. It's a great cage and bolts in easily. Something to think about is that you can remove the door bars, knee bar, harness bar or even the rear diagonal. You can remove any bar you want as needed. I leave mine completely in, as it's mainly a track car and I'm the only one who drives it.

Jim

JackOlsen

I'm a little skeptical of the idea that a harness bar would have as much or more of an impact on chassis rigidity as a bolt-in cage.

1FastRedSC

I decided to go with a safety devices roll bar as it can be changed to a cage quite easily and is made of chromoly. Ultra strong and insanely light, my kinda roll bar, thanks for all the replies.

Bill Gregory

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"><strong>I decided to go with a safety devices roll bar </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Last time I checked (a couple of years ago), the Safety Devices rollbar wasn't thick enough for PCA club racing, if you ever intend to do that. Their rollcage was fine, however, for PCA club racing.

Eric in Chicago

Bill,
I know a couple of PCA club racers using Safety Devices roll cages. I dont know if their roll bars are made of smaller tubes. I do know they had the test holes drilled and the inspection sticker. So I think they may be ok now.

SGOGT4

Jim -

Can you post some pics of your cage installed?

Thanks

M758

My basic custom cage.






I plan to add a second door bar on both sides later this year sometime.

Cory M

A harness bar will not provide anywhere near the stiffness a rollbar or cage would. Harness bars only attach at 2 points and have no triangulation. A lot of them also use heim joints so they are allowed to rotate about their attachment points.

A rollbar can add a reasonable amount of stiffness if it is attached to the car well, the best rollbar would be custom fitted and welded in, attached to the sills and the B-pillar (attachment to the B pillar may not be legal in some clubs, check your rules). You can use the shoulder belt hole to bolt the bar to the B-pillar if you don't want to weld it there.

RedlineMan

Hey;

You certainly don't need it for a street car, and you have to get fairly serious with track equipment before it is makes a difference at the track. Save your bling money for suspension and brakes.

A roll bar will not change stiffness. Not much either will a cage that bolts to the floor pan. In either case, the detriment to your safety on the street - which is significant - is not worth it either case. Street/autoX cars don't need that stuff. If it's a street car, keep it that way. If you get serious enough to have a track-only car, then go for it.

Most of the flex in an early 911 chassis comes from the front unibody anyway. A bolt in cage won't do much for that.