What kind of "flex" do subframe connectors prevent?

[O'Neall]

This is going to sound like a dumb question because I'm not sure I can explain just what I mean... but here goes....

By what kind of "flex" I mean... in what direction? It would seem to me that two bars running lengthwise alone the subframe rails and unibody wouldn't really do much for crossflex (if that's a word... what I mean is flex that goes across the width of the car either straight across or diagonally), but would be better suited to prevent flex that wants to "fold" (like into a "V") the car like a hinge at the firewall.

I don't know if that made any sense, but my point is that it seems to me that preventing this up and down flex at the point of contact is all they'd really do directly by adding strength to that connection. Ultimately that strength would translate to added rigidity which would translate to some "crossflex resistance" (sorry for my lame terminology) I suppose, but it just doesn't seem that without "triangulating" them somehow that SFCs would be much good at preventing this "crossflex" in and of themselves.

Forgive my ignorance and inability to express what I'm trying to ask and explain... but does anybody know what I mean? And can somebody explain to me just what direction of flex SFCs help to prevent

[Boulder69]

Do a search over on pro-touring.com. There are some pretty lengthy threads on this one......

[GM Muscle]

imagine a box.. going from each subframe mounting point up to each corner of the roof.. can you see that cube? now.. take out the four bottom legs and you should have some sort of car port lookin contraption in your mind.haha.. the fire wall will add on leg in the front so put that leg back.. this is basically what your frame setup looks like.. does this structure seem sound? add weight on the out side of the front and back of this box.. seems even scarier to me.. now think if you put two of the legs back on the sides (sub frame connectors) .. plus all the weight being distributed evenly along the floor pans.. it takes that raggedy box and makes a solid structure..i know im probably over dramatizing it but you had the right concept in your mind but you didnt take into acount that your roof is a very active part of your unibody. the whole car including the fenders, inner fenders and floor pans add structral integrity.. but sheet metal can only do so much so when you ask which direction of flex id say all cause it helps complete the structure..

[pdq67]

Short version.

They keep the cab from cracking at the rear window "V"s and also from possibly cracking or popping out the winshield in extreme power use situations like dragging!!

And also the areas just in front of the rear wheel fenders and lower rocker panels from rippling if I remember right..

I do know that my car lifted almost completely rigid after I installed my bolt-on Jegs S/F/C's in front of the rear wheel from the side........

pdq67