Strut Braces- What do you think?

[Silveresrty911S]

Nice bar Matt, which one is it? Was it an easy install?
TIA, Rick

[ChrisBennet]

The old Weltmeister advertisements for their strut braces said that when they measured it, they found the shock towers moved outward under cornering causing a loss of camber. Then they sort of gave the game away:

"The big surprise from Weltmeister's recorded measurement was the fact that only 15% of the camber change could be attributed to shock tower movement. The other 85% took place in the rubber mounts for the top of the shock absorber!"

From this I would gather that the real benefits are from decreasing the movement of the shock inside the rubber mount. A monoball would thus have 85% of the same benefit.
One might ask why you see them on 964/993's and club racers. The 964/993 coil over struts are putting a lot more strain on the strut towers than a torsion bar 911. In the case of coil over cars I bet it makes more of a difference than earlier cars.
Stock class Club racers run them because they are a legal way to crank in more negative camber than the stock strut towers would normally allow. You can physically pull the struts closer together to increase negative camber.
-Chris

[Matt Holcomb]

Rick,

My strut brace is made by Racebred Auto Repairs in Melbourne. The proprietor of Racebred is also my mechanic.

Fitting it took some fiddling as one of my shock towers had moved slightly from years of racing.

The brace cost me $850 AUD, which works out to be approx. $500-600 USD.

It's a quality brace.


Matt Holcomb
MFIWDP
1974 911 Carrera 2.7 (RoW)
Dedicated Homepage
Engine Rebuild Homepage
Pelican Gallery Profile

[dd74]

[QUOTE]Originally posted by Matt Holcomb
[B]Rick,

$500-600 USD.

It's a quality brace.


Matt Holcomb


But damn, Matt: that's a chunk of change for a bar...

I've considered, off and on, a full cage. Gives the chance to run more fiberglass, i.e. the doors.

[tangerine911e]

Everything here is Aust costs normal price x 10. The price of cars is even scarier.

Ash

[Bernd Andritzky]

I´ve made measurements of the tower movement with a laserpointer fixed at the main bar, pointing on a sheet of mm-paper on the trunk floor, taking a digital video of the laser point while driving a slalom course.
Without triangulation the tower movement has been about 3mm, with mounted diagonal brace the movement was reduced to 1mm.
So triangulation seems to make sense in torsionbar-cars, i could also feel less understeering with triangulation.
The strut brace i used for that was from elephant racing.

Bernd

[Matt Holcomb]

David,

I have no doubt that I took one for the team when I said yes to the strut brace.


Matt Holcomb
MFIWDP
1974 911 Carrera 2.7 (RoW)
Dedicated Homepage
Engine Rebuild Homepage
Pelican Gallery Profile

[VenezianBlau 87]

The Weltmeister strut bar and SSI's are the only two "updates" I've performed that had a noticeable effect on performance. The bar tightened up the front top end noticably.

The outside wheel in a turn, hitting a decent bump/hole, sends a shock through the A-pillars that's disconcerting.

This weekend I am rebuilding my entire front suspension since the bar shows the age of the Boge strut inserts. I'm replacing these and all rubber a-arm bushings, sway bar bushings, ball joints, tie rod(s), wheel bearings, and fasteners.

Probably will turn into a bigger project than I anticipate. Especially the wheel bearings.

Bob

[ChrisBennet]

Originally posted by Bernd Andritzky
I´ve made measurements of the tower movement with a laserpointer fixed at the main bar, pointing on a sheet of mm-paper on the trunk floor, taking a digital video of the laser point while driving a slalom course.
Without triangulation the tower movement has been about 3mm, with mounted diagonal brace the movement was reduced to 1mm.
So triangulation seems to make sense in torsionbar-cars, i could also feel less understeering with triangulation.
The strut brace i used for that was from elephant racing.

Bernd

3mm? That would result in a pretty tiny camber change wouldn't it? Lets see, top of shock is a foot and half about the spindle, say 450mm. atan (3/450) = .38 degrees. Maybe not so small after all?
-Chris

[Chuck Moreland]

Originally posted by ChrisBennet
3mm? That would result in a pretty tiny camber change wouldn't it? Lets see, top of shock is a foot and half about the spindle, say 450mm. atan (3/450) = .38 degrees. Maybe not so small after all?
-Chris

I know from past discussion with Bernd that his measures were taken with street tires. DOT-R tires or slicks would increase the cornering loads and surely create an even greater camber loss.

I would argue that coils or torsion bars make no difference. True, the coils carry the weight of the car at the top of the tower. However the force vector of the coil is colinear with the strut, it is not attempting to move the top of the strut horizontally.

In other words, the coil is pushing perpendicular to the strut brace(nearly straight up), and isn't attempting to push the tower horizontally.

[island911]

I would then argue that you have over simplified the differences between coils or torsion bars, and their respective (different) load paths thru the geometry of the structure. . .but I won't.

[Chuck Moreland]

Originally posted by island911
I would then argue that you have over simplified the differences between coils or torsion bars, and their respective (different) load paths thru the geometry of the structure. . .but I won't.

Oh, come on. Enlighten me.

How is the coil creating anything other than a colinear force?

[Randy Webb]

"with a laserpointer fixed at the main bar, pointing on a sheet of mm-paper on the trunk floor, taking a digital video of the laser point while driving a slalom course."

-- Very clever! I love the low buck science in it. Most would have spent $$$ on a strain gage and datalogger - or even more on laser interferometry.

But you compared no bar witha triangulated bar, right? Did you make a comparison with a simple straight tie bar?

Also, what year car was it?

[widebody911]

How about welding mounts to the insides of the trunk, and making a bolt-in brace, that could be removed if need be?

I've also seen cars with a simple tube welded across.

[Chuck Moreland]

Originally posted by Randy Webb
"with a laserpointer fixed at the main bar, pointing on a sheet of mm-paper on the trunk floor, taking a digital video of the laser point while driving a slalom course."

-- Very clever! I love the low buck science in it. Most would have spent $$$ on a strain gage and datalogger - or even more on laser interferometry.

But you compared no bar witha triangulated bar, right? Did you make a comparison with a simple straight tie bar?

Also, what year car was it?

Randy, Bernd's test compared a simple single member strut brace with a triangulated strut brace. He used the Elephant Racing strut brace in both cases, and disconnected the triangulation member for the single-bar test.

The simple single-member brace yielded 3mm movement, the triangulated brace yielded 1mm.

The last time I discussed it with him, he had not performed the test on a car with no strut brace. In fact his setup used the main brace to hold the laser.

His car is an 80s Carrera.

[jyl]

So using a single-bar ER brace (sez Chuck), you get 3mm movement (sez Bernd) which equates to 0.38 deg camber change (sez Chris). Presumably using no brace at all you get more than 0.38 deg camber change (sez me). Is there then even more camber change from the rubber upper strut mounts - who sez?

[thabaer]

Originally posted by Chuck Moreland
How is the coil creating anything other than a colinear force?

You're just baiting us, right ??

Just think about where the force goes beyond where the spring contacts the perch. The various body parts spread out at various angles through metal of different size and strength.

Try this:

Put your elbow on the table with your forearm pointing straight up, then bend your hand horizontal at the wrist so you have an inverted "L". Keep your wrist locked and push vertically on your fingers the way a spring would; it's not the same structure as a shock tower but demonstrates how the loads get distributed.

EDIT: Oh yeah, I forgot to mention to remember the kind of chassis bending vertical force that comes from a stiff shock when you smack a bump. I'm guessing that it can easily go beyond an order of magnitude more stress than springs produce.

[Randy Webb]

Thanks, Chuck.

Now we need to figure out what the extra 2 mm means in terms of handling feel, rigidity, and suspension alteration....??

[Bernd Andritzky]

As Chuck said, i only compared single brace / triangulated brace, because i didn´t see a possibility to measure without any brace in that simple way.
Car is a ´89 convertible.
The differences between no bar / single bar / triangulated bar are really obvious while driving only a few meters on the street.

Regards, Bernd

[RallyJon]

How about welding mounts to the insides of the trunk, and making a bolt-in brace, that could be removed if need be?

That's what I did. The jury's still out on whether the aluminum is adequate, but the brackets certainly are. I really wanted to retain the rubber isolation of the top mounts, so no Weltmeister or monoballs for me.