I'd like to start this by saying that I always thought that such a thing was simply for "bling" purposes, in that due to the proximity of the firewall, that a strut tower brace would have close to zero effect on handling. I continued to modify the suspension of my tC, and in doing so, got a rear upper brace bar (DME, similar to the Ingalls)... and thought, wait a minute... this thing is sitting right above a HUGE lateral brace, and people claim good results.

The firewall is farther away from the front strut towers, than the where a rear upper strut brace sits... so what gives? This is the question that started a whole bunch of learning and logic... and I'm really beginning to think that a strut tower bar should be on the list of items to get for an autocrossing tC.

We'll start by the ever-so-un-credible wikipedia page. Though we all get trained to never accept an open-source document as "truth" without scrutiny, it certainly makes a good point...


Alright, so now we've got a basis for how the strut bar works. I'm sure most of you reading this article is thinking "hmm, fancy way of putting what we already know, but has someone thought out the vector diagrams for this?"

Yes.

http://team99ers.2.forumer.com/index.php?showtopic=702

Coincidentally, this is the reference on the bottom of the wiki page... yet, the logic seems pretty solid. It's interesting to note that most people believe that the strut towers head towards one another during aggressive maneuvers, but in reality, they head away from one another (in a state of tension).

During an extremely hard turn, this can relate to hundreds of pounds of force... (the calculated number was 333 on this M3 at 1g, which a tC is capable of after mods and GREAT tires). This force is pulling on the tire geometry, and could potentially lead to a positive camber shift on the inside tire, which is very bad for a MacPherson setup.

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So, although I haven't given too lengthy of a discussion, it's my belief that one of these things does actually have SOME benefit to it. How much, is tough to gauge, since few of us have the resources of being able to statically produce the constantly variable hundreds to thousands of pounds of force experienced during hard cornering.

Will you notice these effects on the street? No, not if you have any sense to you. You may notice more stability during hitting a pothole (where 2-4g's can be impulsed through the car), but otherwise, you need to be consistently at the cornering limits of the car to notice any "difference."

Are they as noticeable as sways, springs, etc? -- No, since the FSTB doesn't drastically affect the low-speed, low-g handling nearly as much as these major suspension components do.

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For handling purposes, it makes sense to buy the biggest, thickest, ugliest bar with as few joints as possible. I don't know if a "double bar" is any better, provided the ends are welded to the C-brackets, but it certainly couldn't hurt.

What do you have to lose? Hundred bucks, a few minutes' time, and a pound or two of extra weight. But at this point, I'm thinking that's worth it.


Next time we should talk about the rear bar.... as it sits 1.5 inches above a huge transverse beam.

 

well done explaining it..

 

I've heard that sway bars provide a lot more performance than a strut tower bar.

And to be honest, I have the Greddy STB and I didn't really notice a difference when I installed it. My engine bay looks cooler, but it's a pain to change my plugs cuz I have to remove the STB.

 

Well yes, this is true.... but once you own the sways, then what?

This is NOT a "one is better than another" thread, since these two items are not mutually exclusive. Yes, I would recommend getting the sways first, but if someone were in the process of building their car for autocross, then it would necessitate getting both.

I would recommend the sways first, as they are detectable at normal street speeds. You would need to be close to the car's limit to detect any effect from a FSTB

 

nice explanation. it definitely made me understand the concept of how it works better. (especially with the little diagrams on the page referenced)

 

yes i agree that STB's are important. It's just that most people don't really "feel" the difference as much as they do with sway bars!

Doing modal analysis on the torsional twisting/movement of the chassis would be the best, but who has access to millions of dollars worth of equipment and a tC they can twist and sacrifice?!? That's what it would take. but..

In the beginning when the tC came out.. Many had rattling sunroofs and creaks, I found that those with STB's had less than those without one. Sure, it was a problem with the earlier sunroofs, but interesting to note the outcomes of those with STB's. Makes sense less chassis movement means less creaking (if the sunroof was prone to it, which it's been fixed with a slightly different design starting 06+)

A chassis would have to ultimately be completely rigid to not require a STB. Fact is, these cars aren't 1 million dollar cars. so yes there still is chassis movement. Even in the tC's chassis, no matter what people say or believe. They need the actual engineering chassis development rigidity tests to prove it otherwise.

 

^^ so after i installed my FSTB and rear sway, now i get a creaking in my roof when i pull into a place with a rain gutter in the street(where the car is diagonal over unlevel pavement)....im assuming becuase hte suspension doesnt want the take the unlevelness since the sway is not letting it as much....

anyone else heard of this?

 

Definitely...

Another thing to consider, is that people are purchasing C-pillar bars to reinforce the chassis in the center of the "crash cage", yet, they're not addressing torsional rigidity in the spot that receives MOST of the cornering forces, particularly when braking and accelerating.

 

^had a c-pillar bar just made my hatch rattle more and a little more difficult to open/close. My buddy's stock '08 got wheel hop (before the ETD), with the bar where he did not get any before...I also find it kinda interesting that everyone always want to jack up both sides when they put a strut bar on, from your write up it sounds like it would be better to life up one side to but more "collapsing force" on the bar to pre-load to help ever-so-slightly counter-act the positive camber