Well in our car going from just a rear strut brace to this cage we noticed a huge difference in how the car handled. That should tell you there there is flex back there.(how much I couldn't tell you)

I have not been able to get the car to the track yet and even when I do other things would have changed from my last lap time.

I will see what I can do to get some hard testing done but for now you will just have to take my word for it

Ben

 

I don't see any downside to bolting these trunk braces on. Regardless of whether they quantitatively reduce chassis flex, they earn you major style points at the road course.

 

the thing is you don't really tend to get parallelogram distortions in that area of the car... if there were such your car would be coming apart and if there are small ones then the corner strength is enough, cuz they certainly don't break.

the flexes you will see are the bending of the trunk pan and the same for the towers, cuz latteral loads where the grip comes from down low will cause such flexing, concave and convex. such distortions would affect the feel of the car because in a very minute sense it can even change your loaded camber if you get what i mean. if anything more stiff is at least better for predictability.

 

but they also put that bar in the rs :\

 

But there are no suspension mounts near the back of the trunk where this brace ties in, so what could cause that bending? The towers don't provide any lateral location but of course they do carry the full weight of the car plus the vertical component of the cornering loads. If the attachment points for the lower lateral links, trailing link, and upper A arm are rigidly located any other bracing is essenttially a placebo.

Maybe there's something to this, but for the most part the Evo understeers anyway so improving the rear isn't the place to get the big gains. I should probably admit I'm looking at this totally from a road course perspective, drift and rally are completely foreign to me!

Dave

 

Stiffening of the rear chassis will help prevent understeer. It is just like adding a bigger sway bar.

True where the bar mounts in back(near the trunk) is not part of the suspension. Mitsubishi has mounting points already there so they designed the car to have a brace there for people that wanted it.

Connecting these points make both the strut brace and trunk brace even stiffer. There is body flex back there or mitsubishi and race teams would not bother putting anything there to stop flexing. How much I couldn't tell you. But enough that you can feel the difference daily driving not just on the track. That is more then I can say for just strut braces.

Hell we even noticed a difference going from just a strut brace to the cage.

Ben

 

Right on. Even daily driving feels better. It did make a very noticeable improvement in road feel also.

 

I don't believe that for a minute. The point of stiffening the chassis is to have better control over your suspension geometry and make it work better, thus increasing grip. It's totally unlike a bigger rear sway bar which is meant to couple the two sides of the car and increase the rate of lateral weight transfer.

Dave

 

Adding a bigger sway bar will cause the Understeer of the car to be less(this is not what it is made to do but it does do it)

The sway bar is meant to prevent lateral load shifting from the inside and outside tires. Thus planting the tire more on the ground increasing traction.

Thus when you stiffen the rear of the vehicle it does reduce understeer(even though that is not its intended purpose)

If you want to fly to utah we can go take a spin in my car and we can prove this to you.

 

What? That's exactly what a bigger rear sway bar is meant to do! It increases the coupling (makes the suspension "less independent") and make the rear end looser.

Again, that's almost backwards. In a steady-state situation it doesn't matter whether you have a sway bar or not, the amount of weight transfer is what it is. But the greater the coupling the more quickly you transfer the weight.

Stiffening as in increasing the roll resistance, yes. Increasing chassis rigidity, no.

I think I learned a little more from Don Halliday than I will from you.

Dave

 

You probably have

All I can tell you is that on my car with me driving it. It understeered far less with ONLY adding this trunk cage. I don't want to get into a e-arguement with you. But all I can tell you is my personal experience with this. I am sorry you don't agree.

Ben

 

+1. You just have to experience it to know what kind of a difference it makes.

 

i wish i could draw pictures but i guess i'll do my best with a few thousand words.

you mention that the towers provide the support for the full weight of the car plus hte verticle component while cornering. that's precisely what i'm referring to, when your inside is less loaded than your outside then you could have this kind of convex bending of the whole car laterally agreed? now it's not so bad in the mid of the car or even the front because there's little void area and there's the roof, but in the back... there's not only void area but the "roof" (trunk) is not tied in as an integral part of the car but rather as a hinged auxilary.

now the bending would be most pronounced at the most hind end of the car because there's where there's least help from anything else. granted all this is very theoretical and the actual trackable results are rather subjective i think it's up to the person to decide if it's worth it.

for what it's worth, i used to park in this very difficult to get in space and when i used to back out, my rear wheel would hit a bump and i'd literally hear the entire car and paint flex in this bending a piece of balsa wood sound. so the flexing is there ti's just up to you to decide if you want to prevent that first mm of movement.

 

If this was the issue you want a bar that triangulated down to the floor and ran across the two towers, I forget who makes that now, cusco maybe?
A flat bar is just going to bend and deflect under that type of stress, of course if you go to something like a H beam it would help, but triangulation to the floor would be better.
I fail to see how a rectangle is going to help this force be reduced. Actually I fail to understand the train of thought of most all these aftermarket companies braces, rectangles and straight bars are weak by design, a triangle is the stiffest and lightest shape.

 

the straight bar is stronger than the trunk pan by itself. and the triangulated bar is not one piece... the shape is only as good as its design. you're trying to prevent the first mm of deflection not the last.

also... the triagle bar strength is debatable in this application, you're getting strentch that isn't needed and isn't used. what does the triagle do when it's connected to the trunk pan? it doesn't prevent the trunk pan from bending... and it helps minimally in preventing the towers from coming towards each other or away from each other. the tower bar does the brunt there and it alone is enough.

the square is prolly there and this is speculation, because when you're cornering in non steady state the load is not totally lateral, anyone who ever three wheeled can relate. if there is some off lateral or diagonal loading then hte trunk pan will likewise not bend laterally but in an off diagonal way, just like how my car used to flex when i pulled outta my parking spot and my rear right wheel stepped up onto the bump.

the triagle bar likewise does nothing for this eype of diagonal bending. because the trunk section of hte car is like a leg it's flapping around back there with a lotta void area and the triagle bar is right there at hte boundary between the well supported inside and hte not well supported trunk area... making it pretty useless to the trunk in general, the tower bar is good for what it does but adding hte triangle is more mind than work.