Jerry Feather

Why?

upstate bob

yes, inquiring minds want to know.

Speedtoys

Ok.

Why wouldn't this work in either direction, "snug". What's your thinking that something across that area with no play, and "snug" would not service a pull or a push resistance?

I cant see how it would be pulled, and why you would care because...what is pushing down on the chassis to widen that space?

Jerry Feather

If that's the case, and maybe it is, why can't one just install it and tighten all the bolts and jam nuts and call it good? Hans says one should twist the bar so it is "snug," but without saying which way it should be snug. If the bar is not twisted either way to "snug" and it is all tight as a unit, why not just leave it to push or pull as may be required?

I think the real question is, what is the thing there for in the first place?

hacker-pschorr

Speedtoys

I dont know where to start...

But clearly, "snug" is fitting the space between the fenders completely..not pushing them out, not pulling them in.

It's there to help maintain geometry..why do you think it's there?

928NOOBIE

Well I decided it should be snug one way or the other and thought if it was pushing against the mounting bolts it might be more effective.

It was a guess. I will say that I have been back in there several times and I have not identified any movement of the bar when loosening things back up..so I am sticking with pushing it against the mounting bolts for now or until I have information (anecdotal or identified unexpected movement of the bar) otherwise.

Bottom line yes I took a guess.

Jerry Feather

Thanks for that. That is as good as we have at this point.

Constantine

the flyin' scotsman

the bar can be set in a neutral position; neither pulling or pushing as it threaded as Hans describes with RH and LH threads at either end thus after mounting the ends to the fenders the bar can turned then snugged with the respective nuts.

such a great design we are indeed so fortunate to have folks in our circle that can provide such delights.

hans14914

That is correct, the bar is designed to be in a neutral configuration, which is why I use the term "snug" and not tight. There may be applications where a user may wish to provide positive or negative pre-load, and the adjustment allows for this, but as a stock replacement part, the bar should be set to a neutral position whith the car fully settled and on the ground.

The replacement link is incredibly strong, and will not bend. It is actually a suspension component used on Midget race cars, which I just adapted into a cross-brace with quality rod-ends and custom mounting plates.

Setting it to neutral in either a push or pull configuration should make no difference, as the chassis is flexy enough that after a drive, it will settle and be neither, just neutral. This again assumes that the chassis is on the ground and settled when the brace is installed, and the link is adjusted to the point where resistance is just starting to feel noticeable when twisting the link.

To answer a question that will probably come up: "Why make and adjustable brace anyway" - there are several answers. One, it allowed me to take the ovaled slots out from the factory design because the slack can be removed by the center link. Two, its stronger than stock and will not bend. Three, all the components are anodized, so will not flake or require cosmetic maintenance. Four, and this is the real reason I made them, I wanted additional clearance for intake tubes for my supercharger kits. This bar is both slightly raised and the swedging of the tube allows for more flexibility in routing intake tubes along the inner fender. I figured why just limit the brace for my personal use, and offer it as an alternative to the various options currently available.

Thanks for the kind comments,
Hans

Jerry Feather

Hans, that is another beautiful component you have come up with - - and I don't mean anything negative about it in my questioning.

But, it seems to me that neutral is neither snug inward or outward.

What puzzles me about this link is just what Constantine points out, that many of the original links are bent. I also notice that they are made out of very light aluminum tubing, so light that it suggests to me that they might have been intended only or primarily to resist pulling rather than pushing. I can't find myself giving the Porsche designers credit for making them so light duty just to save weight on the front of the car, and leaving them too light to perform as intended.

hans14914

Jerry,

My thought on this is that the 928 engineers always intended these cars to be GT's and as they have aged and people drive them more aggressively, that lightweight bar bends under the stress. I have seen plenty of low mileage cars that have never been driven hard with strait bars. When the cars became cheap, and people felt comfortable driving the snot out of them, we started to see warped bars. The car was a monumental feat of engineering, but lets be honest, it was never designed to be a sports car - it was supposed to be a gentleman's sport GT.

All the fenders and mounts on these cars are slightly different, so there is no way of setting a neutral position before shipping is difficult - which is why the stock bar has slots. I chose a different method of taking up the slack.

GT6ixer

Interesting discussion on whether to set the bar to be pushing or pulling against the shock tower. If the shock towers push in on hard cornering they are putting the bar in compression. The failure mode of a bar in compression is buckling, which is what has been seen over the years as Hans explained. For a given material and geometry there is a compressive force at which the bar will buckle every time. For this reason it's my opinion that if the bar is preloaded to be in tension then the compressive force applied by the shock towers needed to buckle the bar would need to be larger since it first has to overcome the tension preload.

Now this is all a mute point since Hans is using a brace which is sufficiently strong enough to not buckle under any forseen cornering loads. But I guess if you want to err on the side of conservatism you would twist the bar to be snug in the direction of trying to pull against the towers since this will preload it in tension. Just a guess really though, I could have this all backwards.

AO

Hans, can you please post a 26-page installation guide for this? :rooleyes:

Jeebus guys... most of you will never push your car hard enough for this to even be a point of consideration. In fact, most of you could drive without a cross brace installed and never notice the difference. It's a friggen cross brace! 4 bolts. Two adjusters. Done. Move on.