Shock Tower Brace installed, and other

[BBShriver]

Hello all, I just received, and installed my new Rennline shock tower brace (truss style, dual bar). Installed incredibly easily in about 30 min, and made a HUGE difference in driving.
However, in their instructions they did not give any hints on adjusting "preload".
Do I want them pushing apart, or pulling together (seems "tension or compression" has been a debate on here for years..). How tight?

Also got my shifter rebuilt, and installed Weltmeister short-shifter. Again HUGE difference. My shift coupler, and bushings were all worn out, shifting was kinda like stirring soup. Much better now, and much shorter as well.

[jtfreels]

Hey, that looks nice, having a Targa I guess I need one of those.

Search is your friend, look at this thread Installing -Strut Brace - How much to preload

your question has been discussed in the last couple of days.

Jay

[Wickd89]

Here is a thread that I started asking the same question.

http://forums.pelicanparts.com/porsche-911-technical-forum/368638-installing-strut-brace-how-much-preload-post3495337.html?posted=1#post3495337

[911pcars]

A basic question. Why two bars? Is one not rigid enough?

Sherwood

[Dixie]

Why two bars? Is one not rigid enough?

Simple, the cost is the same. One bar works fine. And in some ways better. It's easier to pull the towers together with one bar. But two bars does look flashy.

[BBShriver]

Thanks for the references.
I read through several old ones last night in search, but didn't find either of those.
It seems it has been settled then that the shock towers try to separate rather than collapse? The posts I was reading seemed about 50/50 on people saying different.
I have to say I really don't understand how it's remotely possible that they pull apart.. just seems all backwards, and the suspension guru's i've encountered tend to talk about seing cars come back from the track with the shock towers bent inward (but that was front engine cars..)
But hey, if it's been tested, and proven who am I to argue based on random logic.

As far as the 2 bars... I was actually wondering if it could be intended to load them against each other (i.e. one in tension one in compression??) just in case.
My other theory is with the way it mounts, it should brace the shock towers from any tendency to rotate.
However both of those are both guesses. I do have a technical case in with Pelican to ask about this. Like others, I got the dual bar because it was the same price as the single bar. I have the hardware to convert to single bar if I felt so inclined, but it does look sweet! Feels great when driving too!!

[Wickd89]

There are three axis of motion that describe all possible movement; lets call them the x, y, and z axis. Since you can move up and down these axis, usually this is referred to as 6 degrees of freedom. Back in my old aerospace days this was called 6dof.
The main fix fix of a strut tower brace is to the x axis which is the horizontal plane. The next preferred fix is the y axis (which is along the vertical plan) and that is why a lot of people prefer to add the three-point mount. The third axis is the forward and back motion on the z axis; and this is improved by having the 2nd parallel bar (although it is not that critical and not that big of an improvement because the car is typically pretty rigid in this plan).

Hope that helps......

[BBShriver]

Ok, think I got the tension vs compression issue figured out. While at breafast I did a quick simulation of shock towers pretending my elbows were tires, and arms were shock towers, and leaned into a corner and... sure enough my arms separated.
So apparently yall weren't smoking the crack I thought you were
Now I just have to readjust them for tension... should be easy.

However first I have to install a new battery cable in my Jeep
I hate having reliability issues with the daily driver.... steals time from the toys!!

[911pcars]

Originally Posted by Wickd89

There are three axis of motion that describe all possible movement; lets call them the x, y, and z axis. Since you can move up and down these axis, usually this is referred to as 6 degrees of freedom. Back in my old aerospace days this was called 6dof.

The main fix fix of a strut tower brace is to the x axis which is the horizontal plane. The next preferred fix is the y axis (which is along the vertical plan) and that is why a lot of people prefer to add the three-point mount. The third axis is the forward and back motion on the z axis; and this is improved by having the 2nd parallel bar (although it is not that critical and not that big of an improvement because the car is typically pretty rigid in this plan).

Hope that helps......

For the second bar to be effective in the Z axis, I'd think the space between bars should be more than 1". But you said it yourself, "(although it is not that critical and not that big of an improvement because the car is typically pretty rigid in this plan)."

The dual bar costs the same as a single bar? Perhaps the single bar should be half the price or at least less. IMHO, the second bar is redundant. For a better use of the second bar, fabricate some hardware and fashion a triangulated setup to reinforce the Y axis. Other than that, I have no problem with it.

Sherwood

[Wickd89]

Hi Sherwood,
I agree, one or two inches is not that big, but every little bit helps.
I paid $190 (no tax, free shipping) since I bought it at Ventura Fest.
The single bar was around 30-50 bucks less.

[John Watson]

interesting bar. two weeks ago I installed the Elephant racing basic bar in my 74S. took 10 minutes. I don't know if its for real or just my perceeption, but the car really feels stiffer.

John Watson
74 911S

[John Watson]

when I bought my brace , the instructions said to tighten it 1/3 turn to preload it. I have always heard that 911 strut towers move outward during hard cornering.