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tie rods and strut bars are never going to be compressed to the point of failure. yes steel has a higher fail point under tension, but its modulus (how much it deforms with a given force) is roughly the same either way. the point of it is to strengthen weak points in the chassis, and looking at how the chassis is put together, the point between the tops of the shock towers essentially acts like a stress concentration point, and so putting a bar between these points, to strengthen it, would be much more effective then a lower tie bar, which is just adding to the strength of the already existing subframe, and related lower chassis supports.
also, stabilising the top of the shock towers make the car much more predictable, because it helps stop the shock towers moving around which changes the behaviour of the suspension. this effect is NEARLY unnoticeable on stock sussy, and gets more noticeable the stiffer your sussy. (the stiffer the sussy, the more force it transfers through to the chassis, hence the greater need for bracing)
lower tie rods/subframe braces do this too, but the effect isnt as much, to the point where the subframe braces are largeley used to prevent sway bars from damaging the subframe, rather then to stabilise suspension.
hope this helps!
*disclaimer, i havent tested this myself, just my statics knowlege, correct me if im wrong!
i think your overestimating the amount that steel expands. the coefficient is about 12x10^-6 which means a meter long pipe would expand roughly .000012m, or .012mm per degree, over 100 degrees this grows to 1.2mm +/- .1mm, thats assuming that the engine bay actually gets to 100 degrees.
this tolerance is easily able to be designed into a strut bar (assuming it has been designed to these tolerances), AND the point of a strut bar is to stop the top of the shock towers moving while cornering, or while changing loads are being put on the suspension, which is when a car is constantly running, not when its heating up/cooling down. you shouldnt thrash your car anyway if its warming up.
yes you are correct in saying that the lca pivots are just as important (if not more) then the shock towers, but there is alot more down that end of the car to keep them in check. you'll also find that the strongest front strut brace are 4pt, creating a triangle between the corner of the engine bay, the strut tower, and the firewall.
as far as your question is concerned, can i ask, do you have suspension stiff enough to make a difference?
can i ask? what exactly do you want the bar to do? if your aim is to reduce body roll when cornering, then your best bet would be a sway bar.
and that looks similar to the 4pt braces, though the ones i have seen have a greater angle.
so your concerned about stresses moving into the chassis? with adding the strut bar you are essentially strenthening the chassis, meaning that the stresses coming from the wheel and transferring through the suspension into the chassis, which now includes this strut. the strut takes some of the load, and you end up with less stresses going through the chassis.
remember when the springs are soft (as stock) there is minimal stresses being transferred to the chassis, regardless of the camber of the road. its only once you get stiffer springs that strut bars start making a difference.
Im actually getting both the tower bar and lower tie bar
haven't got the got the lower bar installed yet tho, I'll tell you the handling different once I have them installed if you want :-)
PS from what materials those tower and strut bars use .... if they fail.... thats the least of your worries lol
no, the strut bars arent going to make your shock bolts fail, otherwise thered be a whole lot more warnings around.
less body roll will make the steering more precise. stiffer springs will too, however that sacrifices ride quality which im pretty sure you dont want. other then that, make sure your tyres are always fully pumped (sidewall flex can make your steering seem sloppy) you can look into toe settings, but i dont know enough about wheel alignment to tell you more about that.
I just got a white line sway bar and I'm running stock suspension other then that and stering is much more precise
a 3 point bar is also going to be better, and exposed to more forces than a 2 point.
The 3 point ties into the firewall also, so in that case, it has to resistant some amount of torsional force as well.