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I'm sure its obvious that the problem with specifying that you can only change struts or add a front sway bar is the addition of a sway bar is completely different from replacing parts that wear out. If the rule was the only non-stock parts are those that wear out and obviously would need to be replaced, then there's some logic to that. There's no logic to being able to replace parts that wear out, *and* then add a stiff front sway bar.

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Donnie one more thought. Taking a step back I think the biggest problem in this debate is a misunderstanding of what the strut tower brace is meant to do.

The name of the brace is the cause of the confusion (at least that's how I view it). I don't think there is a road worthy car out there, regardless of when it was made or by whom, where the strut towers actually flex and move. As I said earlier if they were moving there would be visible signs (cracked and flaking paint).

I think the strut tower brace is put across the strut towers because that is a convenient, no holes drilled place to mount it. I believe its goal is to add stiffness to the front of the car across the engine compartment.

Makes sense since that is a huge hole with no support across the top of it. Kind of like the cockpit of an open car. So its the name that is throwing us off.

To me that seems to clarify the whole point of what it is meant to do (add stiffness to the front of the car) and why it has the effects that it does.

R

I'm trying to decide if I want to respond in this thread.

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Karl S.
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Recent trends at the national level have many folks pulling their strut tower bars off from what I've seen. Why? Because they tried it, found no change, and thus concluded they were hauling the weight around for nada. In fact, recent letters are asking for clarification in ST and SP rulesets because the rules on specify allowing them to be ADDED, but not removed or substituted (because cars didn't used to come with them, but recently do, and people want to remove them completely).

And perhaps you're right that adding one will most of the time have the same general effect as stiffening that end of the car would have with more swaybar. Even so, I'd say the only way to know for sure on a given car is to test for yourself in a controlled environment. I don't think you can just go from one event to the next with the change in between. Why? Because for starters the things just don't have that profound of an effect on ANY cars handling built in the last umpteen years. Even those "floppy" cars that won't let the door shut when one side is on a jack.



Sure, and there always will be. We'll never come up with a complete set of allowances in STOCK that won't be that way, either. It makes sense to me that the more allowances you have, the more you do move toward letting any car be competitive. So if you don't like a car du jour kind of setup, well, move away from stock. It's that simple. We can only do so well with limited allowances at achieving competitive balance, and people want a place to play with limited allowances. *shrug*



But now you're changing the argument to SP from stock.


--Donnie

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Donnie when I took the brace off the Talon it was in the same day at the same track with the same basic conditions so indeed I did as much of a controlled experiment as I could.

Thinking more about strut towers to me they appear to be one of if not the strongest sheet metal parts under the hood. A nice cone almost enclosed at the top. I think of them as say a plastic cup. Can almost stand on either end with no drama but will flatten if you even slightly push down on the sides. I'd have to go look but I thought too that they were two layers of sheet metal vs just one for say a typical fender......

Karl, come on now, jump right in! Most of my scars have faded......

Sorry, I thought Wes covered that well enough. But apparently not. That allowance is historical in nature because there was a time when tires started to get a LOT better that a LOT of cars people wanted to compete in became basically unsafe due to lack of roll stiffness. People were worried about flipping cars, basically. So the allowance was added for safety reasons, not performance reasons. It obviously took off for the latter, however, and competitive balance had to be created with that allowance in mind. Now it would be terribly painful to take that allowance back, even though the safety reason really doesn't exist any longer, since so many people have done it and many of those rely on it to keep tire wear at tolerable levels.

Could we have healthy stock classes without a swaybar allowance? Sure. But the transition is what would be terribly difficult and so far the membership overwhelmingly does NOT support that transition.


--Donnie

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Ron, let me take one last stab at explaining my position.

Suspension parts all have specific goals in mind. As we upgrade things, we're trying to make changes that have specific goals, too. But at the core, we need to assume the suspension works in a rigid box because we have no idea how much our cars flex, at what frequency they might move, and HOW they might move.

Without that box being predictable, well, things can get weird. You could find points where going to a bigger FSB stops helping any more because the box just flexes more to counter it. So let's say that point is at a half inch bar. You start going up in bar size in 1/8 increments after that with VERY minimal gains in performance. You end up with a 1.25" bar to get decent. Then you put on a strut tower bar and *bam*, you've over-stiffened and can now drop down to a .75" bar. So in that sense, yeah, the strut tower "stiffened" the car.

But I submit the change was really allowing your FSB to stiffen like it was intended, you didn't stiffen THE SUSPENSION with the strut tower bar. You stiffened the box it works in. I'm guessing this is the kind of thing you felt in your own test. Okay, great. I think we'd generally agree on that.

But I can also imagine a case where stiffening that box could have opposite effects. Some strut tower bars do more than just connect across, they also triangulate to the firewall or other places. And even if we're just talking about most of the stiffness happening in the lateral sense, some cars have a lot more bumpsteer than others, particularly if lowered. Stiffening the resistance to roll can actually keep the car from bumpsteering. But if that bumpsteer caused toe changes that helped turn-in (yes, it can happen), you could end up with oversteer because of that. Stiffen the front, lose the toe change due to the bumpsteer, and lose the oversteer.

Sure, it's a reaction to another *problem* in the car, but if you had no idea that "problem" existed and had actually been helping you to some degree in some cases, well, you'd think you just screwed up by "stiffening" the car. We all deal with compromises in many suspension designs, and this is just another.

So all I'm saying is test it. I don't like general case statements that apply to the "box" that the suspension works in. Yes, I do believe that if your box is too flexible that you need the strut bar. But if you have that, well, you might uncover other problems you have to address, or you might find you had been going the "wrong" way on other mods until you got the box rigid. And I also think the box is pretty stiff on most of the more modern cars out there, so stiffening the box is going to have little perceptible difference nowdays.


--Donnie

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Donnie I think we agree more than not. But we have mixed two different items: sway bars and the strut brace.

I'm not a suspension expert (even though I play one....) so I don't understand how stiffening the box (what the strut bar does) could affect bump steer. I thought bump steer was affected by suspension geometry and the strut brace should have no affect on that at all.

Yes indeed some cars ( older Mustangs?) triangulate the bracing from the strut towers to the front fire wall. LOTS of chassis stiffness added.

But, and here is where I think we are getting things intermixed, the strut bar and the sway bar affect the car in different ways.....even though the final outcome may be the same (i.e. increased understeer).

And indeed I agree 100% that any change should be tested. I did that with a number of cars I've owned with the same results which is why I feel comfortable making a sweeping statement.....for FWD cars! I've no data on how a strut bar would change a RWD car. My gut says it would be the same but I've never run that experiment.

I think you made an incredibly important point which is things must be predictable before you make any changes! So true! And a point I think some folks miss.

Its a lot like learning a track. First, learn enough to drive a repeatable line. THEN experiment with changes to see if they help or hurt. Doing so before then gives useless feedback.

R

The issue is that if the box if floppy, results can be unpredictable. If the box is floppy, we don't know in what directions it is or isn't floppy. We know that adding a strut bar will fix it in one axis, but that's it (unless it triangulates and there are aftermarket bars that do that on a number of cars). Adding that stiffness of a strut bar (or taking it away) can have a myriad of effects, whereas stiffening with a larger bar (or going softer) is likely to only have ONE.

But if that entire box is flopping around, well, everything from toe to camber to caster is affected. And likely all of the above.

So to me, if you had a car where you had the ability under the rules to change a LOT of actual suspension parameters and you noticed a huge handling improvement by removing a strut tower bar then a) you got lucky and b) you SHOULD fix your problem some other way. I'd put the tower bar back and start figuring out what I could do different, because I'd be fairly certain that if I found it then I'd have an EVEN better handling car thanks to better predictability in what my suspension changes did.


--Donnie

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