Strut-tower Brace? We don't need no stinkin' strut-tower brace!

[TBone]

Bump for the new folks.

T.

[jameslk55]

1LE strut tower brace (part number 22756880) – This bolt-on component fits Camaro SS and V-6 models, delivering greater stiffness to the front body structure – a quality that enhances the turn-in feel and supports quicker, more direct-feeling steering inputs.

Maybe the handling benefit can't be measured but the benefits sound good to me. Looks cool too.

[2014CamaroZL1]

The article notes that "aftermarket" strut tower brace are ineffective.
Original equipment is not aftermarket.

[Norm Peterson]

You'd have to test a car with its OE STB and then remove it and test the car again in order to find out whether it is effective. Since it doesn't attach to any more or any different points, there is no reason to expect an order-of-magnitude difference if in fact it's any better at all.

The devil is going to be in the details, so an OE STB may be slightly better than the aftermarket versions if for example the OE bar is either welded or bolted to the towers in two or more planes. But keep in mind also that OE STBs are commonly installed for NVH reasons rather than for any measurable improvements in cornering or handling.

Improvement in driver confidence resulting from the NVH improvements is a whole other matter.


Norm
structural analyst (retired)


Norm

[White_SS/RS]

First, I would have to say that it is a triangulated piece, not the STB itself but as a component to overall triangulation. Really, without it the front suspension is just a V, as seen from the front.

Second, what is NVH, from the stand point of a STB? How does a STB control NVH?.. Dynamic, geometric theory would suggest that during braking the two towers will deflect towards one another. During left cornering the the right tower will deflect inward to a much greater degree than the left, and vice versa for right hand cornering. During acceleration they would relax and pull apart. These are just simplified gross motions of the car, in reality any motion imparted to the strut will impose a direct effect, to some degree, on the structual rigidity of the chassis. These motions could be minimal but they are there. Based off this information a STB should in fact control some of these dynamics. How are these dynamics labled?... NVH! NVH because just driving down the road the front clip of the car will see all of these forces in play at once.

Now that we have established that NVH is in fact flex, or that there is compliance in the front structure lets take a second look at this regarding the convertible. how does the STB help create overall chassis stiffness when it's located forward of the cowl? Technically anything forward of the cowl is a isolated component from anything behind the cowl. Not that it can't have a transitional effect but, you have to realize the STB does nothing to the longitudal (front to rear) rigidity. Seems to me the important areas to address for adding rigidity to a convetable would be in the door and rockers as well as bracing behind the rear seat, floor pan and trans tunnel. In the vert I believe the STB is a structual bandaid. A bandaid that doesn't nesicarily address the overall weakend chassis but cleans up some of the overall NVH. Not the NVH due to the missing roof, because you can't directly address that without putting a hard top back on it but, address the NVH that was allowed to exist, up until then, in every front suspension of a 5th gen Camaro. Clean up the easy to fix front and the 'overall' NVH levels become acceptable. 'Overall' NVH is what the costumer will see, they don't nesicarily care if it's from the front or rear, they just don't want it.

In the end, will a STB help? Yes. Will it hurt? No. Seems like if you have the money then do it. Probably not the best performance value though. To address the $3 million test machine. As long as any flex in the front clip doesn't impart unwanted motion to the steering effect, ie bump steer unwanted caster, camber or toe changes then they will see no problem in it. Fact is, in performance we would rather the strut spring combo do the work not the car structure.

[Norm Peterson]

Originally Posted by 130R

Norm, though I agree at first glance a non-triangulated brace appears suspect, could that be a leftover consensus from a time when chassis' where not as well engineered from the factory as they are today?

No. It would be the other way around, with the older and less rigid chassis benefitting more by additional bracing. All structures deflect when subjected to load. Flexy structures deflect more than rigid structures, and benefit more by adding braces to reduce the amount of relative movement between whatever points are under investigation. IOW, the smaller the relative deflections that would be there without them, the smaller the amount of help bracing between them will provide.

Yes, a brace will always provide reductions in relative displacements between the points that they connect between that can be calculated. The questions then become 'exactly what is/are the benefit(s)', what conditions will the benefits primarily benefit' and 'is it enough to matter'.


Sanity check: lateral loads at the strut tops aren't all that high to begin with - on the order of a few hundred lbs unless you slide it into a curb. And while cornering the two strut tops will deflect in the same direction, meaning that the deflection you're trying to reduce is already only a difference rather than a total. Looks like there is a continuous ring frame from A-pillar around the engine compartment to A-pillar that the tower tops tie into, and this is going to be more effective in holding strut tower deflections down than if the towers were only tied to separate structures cantilevered off the firewall/A-pillar nodes. The diagonal bracing seen inside the right side wheel well also helps hold down strut tower movements.

Anyway, let's assume that you get a whole 1/8" deflection at the outboard strut top and 1/16" at the inboard one. With no brace and a 24" long strut, that's 0.3° camber loss on the outer and 0.15° on the inner. Tie them together such that there is no relative deflection at all (not really possible, but anyway), and you now have both wheels cambering approximately 0.22°. Saving 0.08° camber loss on the outer tire might buy you 0.01g, which most people will never, ever notice.

What tying these two points together also does is change the vibration modeshapes - this is getting into the NVH side of things, and there are many modeshapes covering a wide range of frequencies. Add a brace between points that deflect relative to each other in vibrations by only thousandths of an inch and you'll chase a few of them off to frequencies and to locations where the peak displacements occur that you don't notice as much. This is at least part of where "feeling solid" comes from, and this can allow you to drive closer to the car's limits at whatever confidence/comfort level you need.

The reason I ask is, GM puts them on the verts, and the track oriented cars (ZL1, 1LE & now the Z/28). It seems to me they wouldn't waste the time for no measurable benefit. Let's face it, only GM has done any real study or measure of the chassis' stiffness, any debate on the effectiveness of the brace is merely speculation, isn't it?

Convertibles, which lack the large amount of stiffness provided by a fixed metal roof, obviously benefit the most. Especially when driven hard, or over rough roads (tjink cowl shake here). A car driven at the limits of tire lateral grip will gain a tiny amount by comparison. Not zero, but not a significant amount for most of us either, and it's still added weight mounted up high and up front (and we haven't even started to consider that effect yet).

Is it not possible all that is required for the 5th gen chassis is a brace like the OE brace?

If anything, there is a stronger need to do more than tie only the tower tops together if you really are trying to maximize the ultimate cornering performance. There is less deflection to be "getting rid of" and it's more difficult and more involved to do so. Land of diminishing returns.



Norm

[Norm Peterson]

Originally Posted by White_SS/RS

First, I would have to say that it is a triangulated piece, not the STB itself but as a component to overall triangulation. Really, without it the front suspension is just a V, as seen from the front.

Triangulation specifically requires structural openings to have only three sides, the reason being that triangles don't bend, and stretching/compressing the leg lengths to make one corner move relative to the others takes a LOT more force.

Second, what is NVH, from the stand point of a STB? How does a STB control NVH?.. Dynamic, geometric theory would suggest that during braking the two towers will deflect towards one another. During left cornering the the right tower will deflect inward to a much greater degree than the left, and vice versa for right hand cornering. During acceleration they would relax and pull apart. These are just simplified gross motions of the car, in reality any motion imparted to the strut will impose a direct effect, to some degree, on the structual rigidity of the chassis. These motions could be minimal but they are there. Based off this information a STB should in fact control some of these dynamics. How are these dynamics labled?... NVH! NVH because just driving down the road the front clip of the car will see all of these forces in play at once.

I think I got those points covered. It's not enough to know that these deflections exist (of course they do); you then have to relate their magnitudes to something.

Now that we have established that NVH is in fact flex, or that there is compliance in the front structure lets take a second look at this regarding the convertible. how does the STB help create overall chassis stiffness when it's located forward of the cowl? Technically anything forward of the cowl is a isolated component from anything behind the cowl. Not that it can't have a transitional effect but, you have to realize the STB does nothing to the longitudal (front to rear) rigidity.

In a convertible, a STB tries to cover for what the roof structure in a coupe does. Just not nearly as effectively and it isn't a good substitute, but being better than nothing is really all that is required of it.

Seems to me the important areas to address for adding rigidity to a convetable would be in the door and rockers as well as bracing behind the rear seat, floor pan and trans tunnel. In the vert I believe the STB is a structual bandaid. A bandaid that doesn't nesicarily address the overall weakend chassis but cleans up some of the overall NVH. Not the NVH due to the missing roof, because you can't directly address that without putting a hard top back on it but, address the NVH that was allowed to exist, up until then, in every front suspension of a 5th gen Camaro. Clean up the easy to fix front and the 'overall' NVH levels become acceptable. 'Overall' NVH is what the costumer will see, they don't nesicarily care if it's from the front or rear, they just don't want it.

Agreed; when you're trying to build in or add overall torsional stiffness you're getting into a problem that requires a 3-D solution (deep, wide, closed-section beams or space frames, diagonal plates across rectangular boxes open on the top or side, etc.). At best, a STB provides a little local torsional stiffness, mostly through the small amounts of bending that will be developed at its ends.

In the end, will a STB help? Yes. Will it hurt? No. Seems like if you have the money then do it. Probably not the best performance value though. To address the $3 million test machine. As long as any flex in the front clip doesn't impart unwanted motion to the steering effect, ie bump steer unwanted caster, camber or toe changes then they will see no problem in it. Fact is, in performance we would rather the strut spring combo do the work not the car structure.

There is the matter of 'weight up high and up front" as well as forcing the inboard wheel into even less favorable camber. IOW if we're going to put in a claim for a relatively small benefit we really need to consider the small drawbacks as well.


Norm

[White_SS/RS]

So divulged from the information of the last few posts,.. Is a Strut tower brace worth its weight?! lol

Norm that is a great pic, it shows a lot of the structure where it gets it strength. Also note that it doesnt show a few key items that play a important role. The front subframe is a hugely important item, especially since it is not isolated by bushings. The front bumper, though bolted on it still adds to tie in the lower portion of the front suspension.

Bottom line, GM did an amazing job on this car, some have a STB some dont.

[Norm Peterson]

You might be interested in reading through this paper, which has been around for 15 years or so. Particularly for Cases 3 and 4, where the forward end of the engine compartment was braced in true triangulated fashion in both the vertical-lateral and horizontal planes. They didn't even bother with a 2-point lateral bar only - the stiffness of a 1" tube isn't worth much at all in bending, which is the main loading it would see when the chassis overall is subjected to torsion.


Keep in mind that the % stiffness increase numbers themselves apply only to that particular NASCAR chassis, so I doubt that either your Camaro or my Mustang would benefit to the tune of 33% - 45% if we could actually fit something like their Cases 3 & 4.


Norm

[White_SS/RS]

Originally Posted by Norm Peterson

You might be interested in reading through this paper, which has been around for 15 years or so. Particularly for Cases 3 and 4, where the forward end of the engine compartment was braced in true triangulated fashion in both the vertical-lateral and horizontal planes. They didn't even bother with a 2-point lateral bar only - the stiffness of a 1" tube isn't worth much at all in bending, which is the main loading it would see when the chassis overall is subjected to torsion.


Keep in mind that the % stiffness increase numbers themselves apply only to that particular NASCAR chassis, so I doubt that either your Camaro or my Mustang would benefit to the tune of 33% - 45% if we could actually fit something like their Cases 3 & 4.


Norm

Do the mustangs benefit from any bracing or is it much like the camaro? I only know general info on the mustang.

[Norm Peterson]

It's basically the same situation - the strut tower tops represent two corners of a box that are not braced laterally to each other or triangulated in the same two planes, so the differences are going to be at the detail level (specific dimensions, bracing shape and angles required for clearance, forces, and displacements, etc.). The Mustang might actually be a little shorter from the strut tops to the A-pillars, suggesting it might be marginally less needy of additional bracing.

Anecdotally, there are Mustang folks who absolutely swear by them, and others who swear at them (typically for engine compartment access reasons). More usefully, I can't remember ever reading where Sam Strano recommended adding one to any car. Sam owns a small aftermarket parts business and is a multi-time national autocross champion in both S197 Mustangs and previous generation Camaros, and if he doesn't think there's enough performance benefit for a late model fully streetable car it probably isn't there. Like a few other components on his product list, he'll sell you one if you insist on getting it, but that'd all have to come from you.



This still leaves open the matter of a more solid-feeling car possibly making it easier to drive hard, consistently. I suspect that less experienced drivers benefit more from this.


Norm