Geoffrey

I think the thing that is missing here is that the strut brace should not have an effect on the alignment settings. If you think about the suspension design, the camber is adjusted via eccentric bolts at the bottom of the strut where it attaches to the hub carrier (upright) and the caster is adjusted by an eccentric bolt on the lower ball joint. The bolts where the strut brace is attached only hold the upper strut plate to the chassis and do not serve any alignment purpose. Even the upper adjustable camber plates that have slots that move the strut inward and outward are held fixed by those mounting bolts. The only reason I can think of that the strut brace could have been used to "assist with alignment" would be due to a chassis that was bent or some other serious issue where the alignment settings could not be reached using the factory adjusters.

The early 911 used the top of the strut as the caster/camber adjustment, so you loosened the bolts, slid the top of the strut around where you need it for caster and camber and then locked the bolts. The reason that Larry used the strut brace to pull the shock towers together was to get more camber than the factory adjustments allowed, effectively bending the shock towers inboard.

As for setting the alignment with or without the brace, I don't think it makes a difference. As Larry mentions, the strut brace should be installed with very little pressure, if any, on the strut towers. Installed this way it will not make a difference in the alignment.

I'm curious that the strut brace actually bent...hmm.

Cupcar

Geoffrey-

It would seem to me the optimum value of a strut brace would be derived only if the rubber upper strut mount were replaced with a monoball anyway.

What do you think?

Geoffrey

Agreed. The question becomes "is there any value to a strut bar on a street car?". I don't know the answer. Certainly in a racing environment where slicks and solid joints are in play, the chassis does flex. How much it does on a street car, I don't know.

MarkD

For what it's worth, I think in a cab it does help increase body rigity, even on a street car.
I could easily feel the difference in hard cornering.
Just .02

Though, mine is now banana shaped thanks to the fool who attempted the alignment.
Is there a performance increase with a banana shaped strut brace on a street car?

garrett376

It doesn't makes sense to me how a cab would benefit more than a coupe would (even without regards to whether a rubber-bushed car benefits from the strut bar); I don't see how the roof (on a coupe) would make the front shock towers more stable...

CarreraCup03

I have a strut brace on my track car ... that car is seam welded and has full monoball suspension. The car came with a factory strut brace so I left in on without too much thought. What I did notice is that when I added the strut brace to my 1991 targa ... the mild roof creaking from body flex at low speeds ... completely went away. So it does help stiffen up the front end and minimize body flex somewhat on my targa.

MarkD

Garret, well, the cab body is less rigid overall... so my assumption is that it needs all the help it can get. I would expect that the missing roof introduces flex thoughout the chassis, not just in the center of the car. I think the roof and the front end talk to each other... they are at least aquaintances if not really good friends. I could be wrong.

Cupcar

I was thinking about the rubber mounts some more and it occurred to me that the load transferred to the shock tower will be the same rubber or no rubber just the instantaneous transferr of load would be quicker with a monoball than with the rubber mount.

So, a brace would still make a difference with the stock rubber mounts but theoretically one would "feel" the improvement more with a monoball mount.

Another thing, I think it was measured by Automotion years ago using a dial indicator to look at the movement outward of the shock tower during cornering increasing positive camber.

It seems to me that the shock towers may move inward under heavy braking though, increasing negative camber I wonder if this has been documented?

Dr Strangelove

This thread is right on time for me. I just added a Brey-Krause strut brace to my Carrera Cup car. According to the BK instructions, they recommend "pre-loading" the brace by slightly lengthening it. To my way of thinking, that means putting the brace under a little compression. But that is at odds with some of the recommendations of earlier posters, who felt that a little tension was ok.

Am I missing something here? Also, Cupcar and CarreraCup03 (and others), is there anything special I should know about the Carrera Cup cars relative to the strut brace installation?

Thanks.

-Bruce

Cupcar

Bruce- I just installed the brace with the car on level ground without adding preload in compression or tension.

BTW- I just wanted to point out that all the seam welding done by the factory is at the back of the Cup cars in there area of the transmission hump over the gearbox and in the rear stabilizer bar mount. Anything at the front was added by someone else.

garrett376

Yeah - Automotion probably did this on a 1970's 911 that flexes in a cross-wind

Cupcar

Actually, that picture you show is just to show the water bottle bracket that is on the Euro Cup's and the Euro RS but not on the USA Cup (except the first one built #392) unless added ex-factory.

The actual seam welding is shown here http://www.carreracupusa.org/street/.../Seamwelds.htm

Also the seam welding process is described and pictured in the back of the "Body" book of the factory service manual as well as Adrian Streather's book. There is nothing at the front of the car.

Dr Strangelove

Thanks everyone. I'll adjust to neutral.

-Bruce

jeff522

I've got a brace on my car.When the springs were changed and the car alligned the brace was left on.The shop said thay did know about it.Well on the way home I keep hearing a meatle popping sound.When I got home I took a look at the brace.While not bent it was under a lot of strain.I tried to move the bar but it was locked in place.I undid the brace,which was not easy at all.When it came off the car"jumped".I then re attached the brace and went for a drive.I could hardly keep it on the road it was so far out of alligment.Now when I have any front end work done on her I take it off myself.But it did get me thinking.All that popping going on up front was from shock movement from"normal" street driving.There really is a lot of flex in the towers.While not a total fix it dose help to keep things where they should be.

Dr Strangelove

Holy cr@p. Thanks to jeff552 and 92964cab for sharing your unfortunate stories. Based on your experiences, whenever I take my car in for any alignment, I will remove the brace entirely and then reset to a neutral setting.

-Bruce