ianellison

I have an aluminum strut brace from an RS 964 which I want to fit on my 1990 Carrera 4 Cab. Appreciate help with the correct fitting sequence and in particular the tensioning of the strut after bolting on. I imagine procedure should be:
1. Unscrew horizontal bar so that mounts can be bolted to front strut bolts and tightened down flat to mounts without tension on the bar.
2. Rotate horizontal bar so that struts are under a little tension and pulled slightly together (not out?)
3. Fasten locking rings to hold bar in this position.

Does this sound correct? Comments appreciated.

Millemiglia

A bit OT and I'm sorry that I cannot answer your question but doesn't the strut brace increase the understeering tendencies?

964rh

That's how I did mine Ian
Just watch you don't trap any pipework when you fit the strut end. Don't tighten up the horizontal bar until you have done evrything else up.

Keep the car on flat ground, wheels straight and one side at a time and you shouldn't alter the geo.

Peter

I found the strut brace did nothing to the understeer (neither better or worse) it just felt a little tighter at the front, less flex.

Rob

ianellison

Thanks - But do you pull in or push out slightly the struts when applying a little tension to the bar? Surely on brisk cornering the struts tend to lean into the car so slight tension pushing the struts out would be best?

964rh

Ian

I was advised to tightend up the strut brace inwards (pulling the struts towards each other).

I haven't heard of pushing them out, but would've thought this would have the effect of pushing the wheel to a more + camber.

The way I thought about was the top of the strut, on brisk cornering would actually be pulled outwards if there was movement. Especially on the osf going round a lefthanded corner and visa versa.
The point of fitting a brace would be to keep the struts in the same position at all times.

Or perhaps I'm thinking totally the wrong thing and should have mine pushing outwards.

Rob

Heirsh

This has been discussed before with no agreement on what is best. Some people say set it with the front of the car off the ground. Others say do it loaded normally.

From a fatigue standpoint it is usually best to keep the stress in one direction (compression or tension). In this situation the outside tower in a turn tends to lean towards the outside of the car more than the inside tower leans in, so you get net tension in a simple strut brace connecting the top of the towers. So perhaps it is best to dial in a hair of tension. This would make moot any play the brace has when transitioning between tension and compression (since it wouldnt normally do it) and I suspect is how most are installed. If you put in a bit of compression(lengthening the brace past neutral) when cornering the brace would get less compression until it switched over to tension (assuming the magnitudes allowed this). I don't think you'd want that scenario. Under acceleration the towers will shift the same direction they shift when the car is unloaded.

My recommendation (for what its worth) is to shorten the brace just until you are obviously applying pressure to the towers with the car loaded sitting on the ground normally. Just a bit.

Just my plug nickle's worth. Perhaps one of the hardcore racers will chime in.

MarkD

Inwards but only slight tension. Those bars are not meant to handle compression... they bend.

Ask me how I know

OK, I'll tell you. I took my car into a pcar dealer for alignment (the only work I don't do myself). The tech put so much torque inward that he bent the bar into a banana. Not good. Never got any money out of these fools.
The strut brace is NOT a part of the front susp. geometry and is not to be used to adjust camber. Thought all pcar dealer techs would know that... guess not.

I bent it back.

tafkai

ian ,

imagine (or look on the net for) a fully caged/tied race/rally car .
you will see the cage going through the bulk-head and welded to the suspension tops . then you will see a tube welded between both the suspension tops , mostly this is also triangulated .
this makes the chassis very stiff , so things dont flex with hard cornering .

all we try to do with our strut braces is mimic this to a lesser degree !!!
i have trouble fitting things in my "boot" as it is , without a load of pipe welded in there !!!

so forget about pre-loading the chassis , just have the car sat under its own wieght on flat ground (as you would set the suspension geo.) and tighten the nut when the brace is bracing , and not wobbling about all loose

btw : i'm not trying to teach anybody to suck eggs here , i just thought somebody might be reading this that wants a bit of diy hindsight .

tafkai

http://www.rallyusedparts.co.uk/fullspec/lbesc.cfm
you can enlarge a picture of the engine bay .

tafkai

http://www.staufferclassics.com/74porsche.html

excellent picture here !!! thumbprint above the picture of the open door

if you can imagine that no access to the tank was required , it could be triangulated from say front right of car to front left supension top , and vice-versa .
for access this can be bolted to the main cage to enable it to be quickly removed . obviously this porsche was stiff enough !!

Hoosier_Daddy

Hello Ian,

Speaking from experience, have the strut brace installed while the car is sitting on the ground. If the car is on a lift, allowing the front suspension to droop, you will essentially pre-load the strut brace. My track car recently had a new strut brace installed along with some additional pieces. The technician installed the brace and tightened it down then dropped the car and then performed an alignment. Much to everyone's surprise, we were unable to get more than 2 degrees negative camber on a car that had TRG mono-ball camber plates. Smelling something amiss, I ended up taking the car to a well regarded suspension specialist for a look see and after a little head scratching and while the car was on the alignment rack he openly wondered about the brace "holding out" the camber. Sure enough, once he backed off on the brace the car came in to almost the 4 degrees negative area just as expected.

Good luck and enjoy!

KAS

Trio

The best mental picture I have heard is to imagine using a piece of string tied between the strut towers in place of a strut bar. The idea is to hold the towers together (i.e. tension) not to push them apart (i.e. compression). In this analogy, the theory is that a strong piece of rope would be as effective as a metal bar in achieving the desired effect. Of course you wouldn't use rope in a real application, but it does help visualize the desired effect you are wanting. Hope that helps.

AOW162435

Tom,
To that end, a few on here have mentioned the idea of designing a strut brace that utilizes a length of steel (or stainless steel) cable to tie the two points together. It would use normal mounts at the towers, but be built in such a fashion as to properly clamp/capture the cable. Why? To eliminate the chance of damaging the other tower during a minor shunt to one side of the car. In theory, a stout strut tower bar could transmit enough impact energy to whack the other tower out of spec.

This thinking will only work if you agree that a strut brace only comes into play when under tension.

Andreas

ianellison

Thanks to all contributions on this. I have fitted it with a little tension pulling the struts in a tad. Makes a very noticeable difference on hard cornering and car seems to have lost a tendency (v. slight) to wander on some road surfaces. Thanks again.

Heirsh

AOW162435,

That is what i do on my car. it is currently out of the car because of the suspension parts I was making, installing, remaking, reinstalling, etc. I'll get it back in one of these days.

Its not that the other side doesnt move, its just that the inside tower in a turn doesnt move near as much. There are plenty of pictures out there with a 911 cornering with the inside front wheel completely off the ground. Thinking about it this way it makes perfect sense that one tower moves [outward] more than the other moves [inward].