Rich Sandor

Damien, a cabriolet would benefit more from a rollbar than a coupe. A good rollbar will have at least 4 contact points and tie into, or close to, the frame rail of the chassis, significantly re-inforcing it.

Damian in NJ

All the 968 roll bars I've seen bolt to the floor, so they're stiffening the area inside the contact points. That's not doing much.

Rich Sandor

Not true Damian. A good bar will definately help stiffen the chassis.

I could feel the difference in stiffness from a roll bar in a COUPE. If it makes that much difference in a coupe that I can feel it, then it would even more significance in a Cabriolet.

Damian in NJ

If it's not tied to the frame all it's doing is stiffening up the rectangle of the floor inside the area where the bar is bolted. How can it have much of an effect outside that area?? Do this with a piece of cardboard and some popsicle sticks and see how much the area outside the sticks bends.

FRporscheman

Rich said a "good" bar. A bar that only bolts to the floor is good for keeping you alive in a roll, but it isn't so great for making the frame more rigid. A really good bar will also mount somewhere by the rear wheel well bulge (like where the rear lap belt would be if you had rear seats).

Damian in NJ

Arash, I read past the 'good' bar part. I haven't seen any that don't bolt to the floor.

968workaholic

Its tied to the frame if it bolts into the mounting points for the belts. A roll bar will absolutly stiffen up the car, coupe or cab. Its just more noticable on a cab.

PorscheDude1

I believe a company called Design1 makes a roll bar to address these issues specifically for the cab. It is called a cab chassis brace.
It ties into the mounting points for the for the belts and significantly reduces flex.

The example of cardboard and Popsicle sticks is not good analogy. The floor pans have multiple layers, contours and gussets to improve rigidity.

Lord_Galva

Fight!
Fight!
Fight!

FRporscheman

I didn't mean to offend or upset you Damian, sorry if I did. I'm by no means an expert on cabriolet chassis, I was just offering what I know from owning the 993 cab we used to have.

964/993 roll bars that do the best stiffening, usually have 2 mounts near the rear floor pans, and 2 mounts near the rear seatbelt mounts. Sometimes they mount into the seatbelt mount holes for ease, sometimes they require cutting/drilling/welding.

Borrowed from Pelican

Damian in NJ

No offense taken, and a roll bar can't hurt of course, but if you want a significant improvement bolting it to the floor, or over a small area isn't going to do the job. All one has to do is look at what racer's do.

PorscheDude1

Like this?