Are they really necessary ? I've seen some pretty tough cars that don't use them and some fairly tame cars that do have them. I'm just wondering what the wise men out there have to say.
To brace or not to brace THAT , is the question!

I got one to keep some rigity in my front end, witnessing my brothers SR turbo ute torque i can imagin that body twist could be a problem. i would imagin that it would be much harsher on the suspension, therefore making the suspension do what its meant to do, ideally eliminating twist and flex within the strut towers and making the suspension do it. thats my idea behind it, what about you guys?

im with 2qk4u on his opinion, but seeing as though my ute will have a standard a12gx i cant see flex being a prob in my example, so its really just to make the engine bay a little nicer to look at(read- showpony)

Having a brace can not hurt. Even if having a A 12 motor, under tight cornering you will flex that body. A more powerfull motor like an SR20 would make it flex even in straight line, just by the rotation tendency an engine has under load. But make no mistake, swift cornering flexes your frame/body, and a tower brace is insurance against losing precious energy in fighting the opposing forces that create flexing and torsion. Put that energy where it belongs, by installing a tower brace.

You want to know how much a 1200 can flex through hard cornering, push your finger in the gap between the door window frame and the roof while going through some twisty stuff. I dare you!

engine bay bling my shiney ones are anyway

if you are pushing your car that hard thru corners with a damn sticky tyre, and still managing to keep it on the road, you may notice a little difference between with or without, if you rally and jump your datto regularly you may also notice a little less inward flex of the towers, and your alignment may last a little longer.
the firewall and the bulkhead will take the most of the twist ... how successful this is also depends on how much rust you have in the engine bay

I will have to go with Pierre with this one too. A racer friend of my dads told me the same thing about a tourquey motor distorting the strut towers.
I dont know weather my car will have any problems with it but I have made one up just incase "read 'showpony'".
It is made from two Falcon torneu? cover holdy upy things, so it has a nice curve to it. Ha, as soon as my engine bay starts to twist, my welds will probably all give way

it's not so much weakness in the strut towers that'll let them flex its the chassis ... or lack of in the case of a datsun ... that allows the motor to twist the body so much ...
all big hp cars will suffer from chassis twist under a big launch/acceleration, watch with drag cars, generally one wheel will lift alot higher that the other depending on chassis strength, the addition of a tower brace may help in the situation but they were originally designed as a suspension component not a body strengthener

i had a mate who fainted at the wheel and wrote of his 1600. He hit a brick fence with the front corner and the car crumbled but the strut tower brace held its own. Safety too! what more could you ask for?

My 2 cents.........
Horses for courses.

I reckon a bit of body flex isn't a bad thing.
However, If you're regularly pushing hard then the constant flex can result in the chassis welds being fatigued. Possibly resulting in structural failure. $$$$$ Ouch!

This is where a strut brace comes in........
But. (there's always a but) If you're running poor quality suspension setup, I reckon a strut brace accentuates ordinary suspension performance by taking the flexibilty out of the chassis & forcing it through the suspension.

If you're racing regularly or just like a bit of bling.... Go for it, but I reckon they're not necessary for normal street use & the occasional track day.