I'm not going to argue the effectiveness or lack thereof for a 2-point strut tower brace on a modern (ie: STIFF) chassis like the S197 or S550... but saying that you did a "test" by a single autocross run on/off, or "felt no difference" is hardly a "TEST". Let's be honest with ourselves, and watch our word choices.
I'm not saying that these opinions are irrelevant, and
I don't even disagree with them, but please do not confuse opinion with real testing or scientific data. This is the problem I see with social media and forum responses much of the time... impressions, feelings and buttdyno opinions often become repeated so often that they can effectively become "fact".
Just... please be careful with the word "test".
I've had the factory 2-point braces on two of our heavy track Mustangs, including our S197 at the top and our '18 GT S550 above. I am of the opinion that if Ford decided it was worth the cost and weight to add these simple braces, how can it hurt? The strut towers DO take a tremendous amount of suspension loads through them.
Now on some builds we will add a STB simply for
aesthetic and convenience reasons - they can often make a great place to hang shock reservoirs onto, which need to be kept away from heat sources and easily reached for knob access.
On some chassis with weak strut towers (BMWs!) we will
always add a STB, to reinforce the thin, weak strut tower sheet metal. We've see these towers crack when going over big bumps in these cars without an STB.
In a modern S197 or S550 Mustang? NEVER. Multiple layers of really beefy American steel.
In the end, keep things in perspective. These STBs do not weigh enough to worry about, either way. We are talking about 3600 pound cars and the 2-point Ford brace above weighed in at a whopping
5.1 pounds. That is a .13% change in weight. Also known as a ROUNDING ERROR...
On the S550 there is an optional 3-point component to the factory GT350 brace, shown above. Its another 10.6 pounds, for a
combined total of 15.7 lbs. Again, not a big number on a 3600 pound car. This car has a LOT of metal in it.
We never even ran our 2018 GT with the extra 10.6 pound black plate steel piece, but we're putting all of the STB bits on our 2015 race car build (see above - build thread in the Vorshlag sub-forum). Why? Well... with 335mm Hoosiers loading up the strut towers + aero loading, it is just
cheap insurance. We are cutting out large amounts of metal elsewhere, too... that is how significant strut tower suspension loads are
Now I am in no way advocating that the S197 and S550 track rat drivers here in any way NEED to buy a 2-point or 3-point strut tower brace. For most of us here there are better ways to spend $100-300 to make our cars faster. Other than convertibles (which are
hugely compromised in torsional rigidity) these ultra stiff
modern pony car chassis don't really pick up anything from the PLETHORA of bolt-on doo-dad brackets, braces and plating that so many Mustang suppliers sell. We can point to many of these parts as a symptom of the diesease called "STEELITUS". Why do so many braces and reinforcements get sold? BECAUSE MUSTANG OWNERS WILL BUY ANYTHING.
Some of these doo-dads can come in handy, however, like these Watson Racing jacking point kit on the S197 race car above. These are handy AF if you need to do a FAST tire change on one side of a car. It was stitch welded in, of course.
Same thing goes for "jacking rails" like the ones on the S550 Time Trial shown above. I doubt there is any noticeable "chassis stiffness" added (opinion!), but they are a
convenient way to jack the car and
not crush the pinch welds on the chassis. If you change tires a lot it might be worth it for you - again,
comfort and convenience, not performance.
I just wish the companies that sold these doo-dads marketed them like this, more honestly.
Cheers,