Myth vs. reality: Strut mounts, camber braces, monoballs, rubber bushings, etc

[sugarwood]

I removed my Weltmeister Camber brace b/c I simply wanted more room for bags.

I basically read that this strut bar really doesn't do much.
I also read that for basic street driving and some casual DE, a strut brace is placebo.

Is anyone inclined to explain the general concepts involved?

1) What is the monoball strut mount upgrade about?
What limitation or shortcoming of the stock strut mounts does it remedy?

2) I heard that a strut bar doesn't do anything on it's own,
but only makes sense in concert with other suspension upgrades.

3) The strut mount's rubber bushing is what allows play, and a strut bar does nothing to address this inherent play.

4) The Weltmeister Cambermeister somehow "locks" the strut top which is bad? Can someone explain this in layman's terms?

5) Does the putative benefit of a strut bar apply to basic street driving? Or green level DE?

[Cajundaddy]

In broad terms, the more tire you put on the car, the more lateral G you generate, and the more things need to be tightened up to precisely control your contact patch. Springs, sways, monoballs, strut braces are all tools to help control the contact patch, and some cars need more help than others. All of it is a system and a really well developed car has chosen these components very carefully to compliment each other and the car as a whole.

For a street car on street tires, honestly most of this stuff is bling. For a dual purpose street track car, springs, sways, increased camber, and strut brace might make sense depending on the driver level and tire choice. Careful choices here will result in a chassis that is more precise and less forgiving than stock.

In a fully developed race platform, max precision is desirable while maintaining drivability. If everything is so tied down that chassis twist becomes your spring rate you have gone too far and the car skips like a stone.

It's complicated. I hope this shed a little light rather than clouding the question further.

[Flieger]

The Weltmeister Camber thingie is bad juju because it locks the top of the struts. If you look at the way the suspension is configured, the only way the wheel can go up and down is if the strut pivots slightly at the top. By locking that down you are forcing your brace to bend and or the top of the strut to bend anytime you want the suspension to move. This puts extra stress on the strut linear bearings, causing more friction, which is the enemy of both ride and handling.

[gliding_serpent]

Joining in here because my car came with a cambermeister. I have not thought about it much. Post #2 says it all as far as what is needed, and why.

Here is Weltmeister's spiel on things:

"The design people at Weltmeister built a testing device to record shock tower movement under load. Their tests revealed a surprise, shock towers do not collapse inward! Rather, they spread apart under hard cornering. The cornering force from the tire’s contact with the road, up through the strut, acts like a lever pulling the top of the struts apart. Only 15% of the camber change could be attributed to shock tower movement. The other 85% took place in the rubber mounts on the top of the shock absorber! The Cambermeister design does it all—prevents shock tower separation or compression, as well as preventing 90% of the movement in the shock mounts. Tests prove that Cambermeister limits shock tower movement to only .002 - .003 of an inch! Cambermeister bolts in and removes easily; there are no holes to drill, and it’s fully adjustable with top grade, teflon-lined (quiet) rod ends."

My view is that with uprated suspension and stiffening, there is a level of harshness that is going to come with it. Gain in one area at a cost to another. Part of the game. I don't understand the geometry of the Porsche front suspension to understand why this prevents the wheel from going up and down, but post #3 sounds legit. I don't think I am going to remove my cambermeister however. With bilstein sports and 22mm sways, 22/30 torsion bars, I am satisfied with a suspension that is street friendly, track capable. Mind you, next winter suspension is on the top of my list to evaluate and optimize, so I appreciate this conversation.

[sugarwood]

Ok, so the top of the strut has a rubber bushing to presumably allow for some play, right? On other cars I've changed shocks on, both the top and bottom of the shock are bolted down. Wait, this must be a shock vs. strut thing, right? The strut is a structural part of the vehicles suspension. Why do you need play at the top of the strut? And is this what the monoball strut mount addresses? By removing the rubber bushing, there is less play?

[uwanna]

Originally Posted by sugarwood

Ok, so the top of the strut has a rubber bushing to presumably allow for some play, right? On other cars I've changed shocks on, both the top and bottom of the shock are bolted down. Wait, this must be a shock vs. strut thing, right? The strut is a structural part of the vehicles suspension. Why do you need play at the top of the strut? And is this what the monoball strut mount addresses? By removing the rubber bushing, there is less play?

The rubber provides vibration and harshness isolation for a nice smooth and quiet experience in a nice civilized GT road car. Monoballs are great in track cars for a precise suspension, but will drive you crazy in a daily driver! Many Pelicans have installed monoballs thinking it was an upgrade, put subsequently removed them, citing harshness!

[onboost]

Originally Posted by Flieger

The Weltmeister Camber thingie is bad juju because it locks the top of the struts. If you look at the way the suspension is configured, the only way the wheel can go up and down is if the strut pivots slightly at the top. By locking that down you are forcing your brace to bend and or the top of the strut to bend anytime you want the suspension to move. This puts extra stress on the strut linear bearings, causing more friction, which is the enemy of both ride and handling.

Maybe I'm confused with the name but the Camber Miester I assume is the strut brace and does not lot the top of the struts. All it does it tie the structural towers of the tub. The struts are still free to turn/pivot etc.. in their mounting.

Originally Posted by uwanna

Monoballs are great in track cars for a precise suspension, but will drive you crazy in a daily driver! Many Pelicans have installed monoballs thinking it was an upgrade, put subsequently removed them, citing harshness!

There's your bad juju.. for the street! Monoball is just as they say, a spherical ball/or bearing, thus it is metal to metal.. mounted in a metal plated and bolted to your metal shock tower.. The rest is basically as described by uwanna.

[uwanna]

[QUOTE=onboost;8939827]Maybe I'm confused with the name but the Camber Miester I assume is the strut brace and does not lot the top of the struts. All it does it tie the structural towers of the tub. The struts are still free to turn/pivot etc.. in their mounting.
QUOTE]
Yes, the weltmeister strut bar LOCKS the top off the strut to the bar. Very questionable design IMO. Most Pelicans that use them have modified them like the lower pic to eliminate bolting them to the strut. Being bolted to the struts caused them
to tear the welds of the mount apart and didn't appear provide any benefit!

[sugarwood]

Can you clarify the bad juju of the Cambermeister immobilizing the top of the strut?

[uwanna]

Originally Posted by sugarwood

Can you clarify the bad juju of the Cambermeister immobilizing the top of the strut?

Well tearing up the weltmeister mount welds for one, plus the strut rubber mounts
are meant for vibration isolation, which is defeated by essentialy bolting the strut tops
to one another. Kinda like the monoball problems.

check this thread:
Weltmeister strut bar,cracked bracket

[VFR750]

Originally Posted by uwanna

Yes, the weltmeister strut bar LOCKS the top off the strut to the bar. Very questionable design IMO. Most Pelicans that use them have modified them like the lower pic to eliminate bolting them to the strut. Being bolted to the struts caused them
to tear the welds of the mount apart and didn't appear provide any benefit!

Agreed, cutting the upper mount helps, but you should then change to a camberplate with mono-ball pivot verses leaving in the old rubber mount bushing.

I went with a narrower camberplate and preloaded the towers inward a little. I can get -2.5 degrees camber.

A car with Mono-balls, stiff springs, thicker swaybars and hard bushings is an acquired taste. Acceptable on reasonable streets but certainly harsh. Very predictable and responsive on the track. I've accepted the street compromise for better handling on the track. I just avoid rough pavement.

If you are not doing much track driving, then you may just leave it off. Street driving is not going to uncover the need for a lot of negative camber or expose excessive camber change.

[BFT3.2]

I can only speak for MY experience and not commenting on anyone else's. Last fall after I rebuilt/refreshed my entire stock/original front suspension and steering rack, I felt ZERO added harshness from installing monoball strut mounts and the roads by me a far from perfect. Maybe because I did the whole lot (22mm front TBs, revalved Bilsteins, turbo tie-rods, sway bar bushings, Rebel solid A-arm bushings etc.) that the cumulative effect has the suspension working better as that was the goal. Any new vibration in the body is also prob isolated from me/my butt by the seat. Would rubber strut-top mounts isolate it even more? Im sure to a degree it would but unless you constantly drive on the roughest roads the vibration wouldn't really exist to much in the first place. Im not even advocating mono-balls for street-only use, just relaying my experience with my car.

On a similiar topic, I recently installed Rebel poly engine mounts and that clearly had a immediate effect of slightly increased felt vibration.

*edited

[VFR750]

I would agree the monoballs by themselves should not be a big difference. Especially if your shocks work properly.

Noise in the cabin probably goes up.

[Bill Verburg]

The strut tops absolutely have to be able to move independently of the chassis and each other.

Here's a 911/930 front end sans chassis

As the wheel moves up or down the angular relationship between the shock top and the chassis and between the 2 shock tops changes. That's why rubber or a uni-ball is used there.

For those that don't know how these work here's a pic of the uni-ball itself. The inner part is free to rotate in a fixed shell, the fixed shell has a thin Teflon pad, the striped inner part here, that facilitates smooth unrestricted motion. The shock rod is solidly captured by appropriately sized bushes to the inner ball part and the shell is captured solidly by the chassis via a plate.

[sugarwood]

That is a great photo, Bill.
I'm trying to understand why the stock top needs to be able to move.

1) you hit a bump
2) the wheel gets pushed directly upwards
3) the shock compresses

Why does the strut top need to move?

Actually, since that A-arm connected at the bottom is a fixed length, the wheel can not simply go straight up, right ?
It would sort of have to pivot rotate around the radius of the A-arm, if that makes sense?
Like in theory, if that torsion bar A-arm was pivoted upwards 90 degrees, the tire would have to be flat horizontaL.
As the wheel goes up, it will have to angle inwards and the outer part of the tire loses contact with the ground?

Is this the central idea behind "camber" ?
Does having some play at the strut top help counter this camber issue?
Either the tire rotates inwards, or the strut itself needs to adjust, so the tire can stay planted?

[Sicklyscott]

That's how I understand it. Of course pivoting in/out depends on ride height and how compressed the suspension is already. The position of the control arm will determine all that.

[Flieger]

You don't need "play", you just need rotation- hence a monoball is used there. The spindle/wheel axis is welded to the strut. As the wheel moves up the strut compresses and it rotates about the top pivot because the control arm is following a curved path at the lower ball joint. The thing the monoball eliminates is the radial compression/deflection of the rubber bushing, which contributes to the wheel being able to depart from the camber curve defined by the control arm/strut relationship when a load is applied.

In other words, when you are cornering the force between the tire and the road causes lots of flex in various bits. The sidewall flexes, the rubber bushings compress, the metal parts deflect, etc. in about that order of importance. All of these deflections cause the wheel to try to lean out at the top, which reduces your cornering force or requires more static camber which has consequences on braking ability and tire wear.

The reduction of deflection is the reason why low profile tires came about, as well as the use of spherical bearings instead of rubber bushings. Having said that, deflection is not always bad. Newer cars use rubber bushings with different stiffnesses in different directions along with complex linkages to provide vibration isolation without impacting handling too much. The 918 uses rubber bushings in places. Porsche was a leader in this, developing the "Weissach Axle" for the 928 which caused the rear wheels to toe-in under braking, adding stability. This is the opposite of what the wheel wants to do.

[Flieger]

Full disclosure: I have monoballs at the top of the strut and inner trailing arm. I have Rebel Racing bushings for the front control arm and rear spring plate. I have 22mm front and 31mm rear torsion bars.

[VFR750]

I think you answered your basic question. The a-arm does cause the angle of the strut to change. And if you made the upper connection really stiff, the next softest thing would have to deflect or bend. That might lead to wear between the strut insert and the strut itself.

So, yes the upper joint needs to move. A monoball is the most movable, with the least amount of friction, and least amount of unwanted deflection. The rubber deflects more and changes the relationship between the tire and road more. Not terrible, just more.

[gliding_serpent]

It it the cambermeister design that is bad, or the combo of the cambermeister and the monoball?

And at what point does this become a failure point? Hoosier grip? R comps? RE11 or other high performance street tires?

Weltmeister strut bars

Might be an excuse to use my new metal drilling kit/die tapping kit again.

Originally Posted by 911pcars

Back when WM developed their strut bar, the thinking was that their setup would decrease chassis flex by fixing the upper strut to the chassis. Along the way, some folks theorized that fixing the upper strut to the chassis places undue stress on the strut unit itself, and probably exacerbated with the introduction of the varioius rigid spherical bearing products that replace the rubber mount.

Some owners enlarge the center opening of the WM mount bracket to allow the upper strut to do its thing. IMHO, the C-shape modification to WM bracket shown above may have compromised its rigidity.

The one I modified has a larger center hole to clear the nut OD:





Sherwood

Originally Posted by Innov8

OK, I finally am getting back to my task, I measured the impact socket around the 22mm nut and if I cut a 1-3/8" hole in the center of the bracket, I should be OK to mount this strut bar without restricting or over-stressing the strut bolt (as described above).


While measuring the brackets, I thought...others have found cracks (see above post links) in their brackets? So...I look and there they are! Nearly equal length cracks at the bend of the metal on both brackets...on the leading edge side of the bracket. Look for the black arrows I've drawn on each bracket.