Strut tower brace adjustment?

[bship]

When attaching the tower brace, do you want to tighten the bar by pushing the ends away or by pulling them closer? There is only negligible distance gained or lost either way so it may not matter? I hope this makes sense.

Thanks
Scott

[Formerly Steve Wilkinson]

Unless I did it backward--always a possibility--you want to tighten the bar by making it try to pull the strut towers imperceptibly toward each other. Under cornering loads, the struts try to push >away< from each other.

Stephan

[bship]

Thanks, I had tightened the bar as much as I could pushing away from each other, so I will make the correct adjustment.

Scott

[kqw]

bship....

it's called pre-loading the brace... this is done by rotating the brace tube in the direction that LENGTHENS it by 1/2 turn..I.E>

Be very careful, you can rotate the tube several turns with little resistance and put enormous force on the strut towers, therefore DO NOT exceed 1/2 turn from the neutral position....

[no substitute]

Lengthen? Wouldn't this facilitate a slight spreading of the towers by an amount equal to whatever distance a half turn is equivalent to?

[Formerly Steve Wilkinson]

I look forward to seeing input from...well, I don't know who, but somebody authoritative. My understanding is that cornering loads want to spread the towers, so you pre-load the strut brace to counteract that by trying to slightly pull them >toward<, not away from, each other.

But what do I know?

Anybody?

Stephan

[kqw]

What I mentioned earlier......

I am sure Quote: "Somebody authoritative" in the know will confirm.....

Think about the terms: Pre-Load vs. Counter-load....

For example:

Brey Krause who manufactures one of the best strut tower braces on the market.... www.bkauto.com

Check Pre-loading instructions.....

and there are several other sources that will confirm how to pre-load a strut tower brace.

But, what do I know....

Thanks...

[Zeke]

Originally posted by Formerly Steve Wilkinson
Unless I did it backward--always a possibility--you want to tighten the bar by making it try to pull the strut towers imperceptibly toward each other. Under cornering loads, the struts try to push >away< from each other.

Stephan

I would have thought that the towers would tend to move in the same direction, toward the outside of the corner. One (the outside tower) maybe a little more than the inside. All this does for me is add reason to buy the trianglulated model.

And, I would tend to agree with Wilkinson. Others have even posted that they were trying to pick up a fraction of negative camber, hence, shortening the bar from neutral.

Now, we will hear from Moreland (I hope).

[RoninLB]

fwiw, MMarsh did a good post on properly choping the bar mount. has something to do with the poor design of most strut braces, especially the Welt.

[Randy Webb]

In the Automotion catalog (where we bought parts before the Internet, before Pelican, and before Perf.Prods. bought them out), there was a stmt. that ...[Weltmeister] I think, had actually measured the towers during cornering and found that they tended to move out -- away from each other. It did not say how they did it.

There are numerous ways to do this however: one could use a laser interferometer (if you happen to have one in your back closet) to measure even a very tiny distance change (B&W has used these to measure cone breakup on loudspeakers). Or you could hook up a strain gage between the towers - on the strut bar itself.

Some of the really hot ME's on this board could prodcue truly authoritative results -- things that could be published in an ASME journal, if they were so inclined (or paid). ....

If we are going to use the standard of truly authoritative we are going to have to see the methods described. A mere opinion by an expert won't meet that standard.

Of course, you can just put one on and turn until there is the tiniest pull and not worry too much -- that's what I did. Someday, I'll have to disconnect it and compare with having it in.....

[Formerly Steve Wilkinson]

Well, MEs or not, I went to my go-to guy Steve Weiner, who builds some of the best 911 racecars and high-performance street 911s in the country, and he said it's ultimately six of one, half a dozen of the other, as long as you take any looseness out, whether by setting the bar in tension or compression. He does it the way I do--slight tension setting.

Stephan

[no substitute]

I would assume it desirable to pre-load the bar in the direction that counters what the towers want to do under load. It is also my understanding that the towers want to spread, so I took up any slack in a shortening direction. If it is the tendency of strut towers on vehicles other than a 911 to collapse (toward one another) then a lengthening pre-load would make sense. Zeke is probably correct that the towers tend to go the same direction, but they also in all likelihood separate at the same time.

[Randy Webb]

slight tension is what my last para. states.

[LARRY SHARP]

weltmeister braces were developed with the assisstance of Dwigth Mitchell. They had a indicator with a tattle tail needle that verified the towers pull apart under cornering loads

[stlrj]

Why not try it both ways and see if you can tell any difference objectively?

Joe

[Zeke]

Originally posted by LARRY SHARP
weltmeister braces were developed with the assisstance of Dwigth Mitchell. They had a indicator with a tattle tail needle that verified the towers pull apart under cornering loads

And I'm going to agree. My postulation is that the outboard tower moves more than the inboard one due to the fact that the weight transfer is one the outboard wheel applying more force to the strut than the lighter inboard side. So even if they are going in the same direction, it would appear that they are spreading. The only way to verify this would be to use some of Randy's techniques isolating the towers.

Either way, a brace seems like it would help, but I'm still convinced that the triangualted one is the one that will do the most good in eliminating camber change.

Where's Chuck?

[Randy Webb]

LEt me muddy the waters here a bit more. Somewhere - maybe in his book - BA states that the tie bars (or "braces") don't really help the early 911s much.

so ..... (?)

[Chuck Moreland]

Originally posted by no substitute
I would assume it desirable to pre-load the bar in the direction that counters what the towers want to do under load.

Exactly! Otherwise you are encouraging the towers to move.

On the triangulated brace, I recommend the horizontal brace to be in slight tension. The diagonal brace should be set neutral since it sees both tension and compressive loads depending on which direction the car is turning.

[Formerly Steve Wilkinson]

Yes, Anderson does say the strut bars don't help early 911s. My information is that he's wrong and that a bar can have a tangible effect on the sharpness of turn-in particularly. It happens, though with the esteemed gentleman Bruce, who I know and respect greatly, it's rare.

Stephan

[stlrj]

tangible effect on the sharpness of turn-in

The effect is likely due to the toe out induced when pulling the towers appart due to preload. The same effect could be had by adding toe out without the need of the brace.

Cheers,

Joe