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TB Performance Torsion Bar
I am intrigued by why and how this bar works the way you state Iso100. Stiffening up the rear generally tends to add more oversteer and yet it seems that has been somewhat dialed out. I know you say the the rear can still break loose, but at much higher tolerances, which again leads to the idea that you dialed out some of the engineered oversteer.
You are stating that this mod keeps the tires flatter on the pavement? Isn't that opposite what a traditional RSB does?
You are stating that this mod keeps the tires flatter on the pavement? Isn't that opposite what a traditional RSB does?
I've got the TB torsion bar, 6-point Pierce and a mid-brace on the way from Pierce. Yes, you read that correctly. Jim fabbed up mid-brace for me. My MBRP was hitting the OEM brace. I should have it Friday and I'll be getting plenty of pictures so they can add it to their catalogue. Also, Koni STR.Ts have been installed. Unfortunately, I haven't been able to drive the car as I'm waiting on my turbo to come back in, and then my 2JR intake... I'm getting off topic. Anyway, I'm planning on this car having a completely different ride feel.
Thread Starter
#33
I'm with you. Generally, stiffening the rear does either add oversteer or reduce understeer.
I believe what's happening is that there's less body roll/lean when under high loads. This, in turn, keeps the tires flatter on the ground for longer instead of rolling up onto the outside edge and reducing the contact patch.
I wouldn't say that "keeping the tires flatter on the pavement" is the opposite of what a traditional rear sway bar does. An anti-sway bar's main goal is increasing roll-resistance by more solidly connecting the left and right suspension together. When the right side compresses up, the bar transfers the same torque to the other side, pulling up on that side.
Additionally, this has the effect of increasing apparent spring rates while under cornering loads because any forces compressing the suspension on one side are transmitted to the other side via the bar. While going straight, the suspension will usually deflect upwards while together and just the normal spring rate will be in action, not the additive forces via the bar.
Even with the car seemingly oversteering less, ultimate grip is raised and it certainly doesn't understeer any more than normal unless you try to get it to. I'm not sure what the secret formula is for getting the rear end to step out even more than stock but I imagine it might be an increase in rear spring rates without increasing the stiffness of the twist beam rear axle.
Once I have had more time to really push the car at the (new) limits I'll be able to comment on exactly how it behaves. I have driven the car hard through turns on roads I know well and the limit is definitely starting to be higher than I feel safe trying to find on public roads. Until I know how it breaks free when it decides to finally let go I'm not going to try my luck.
Put it this way, there's a particular S curve on a back road that I can normally take at 63 or so (35 limit). Yesterday I drove it at 70 and the car was planted and sure. Not even any tire noise.
I believe what's happening is that there's less body roll/lean when under high loads. This, in turn, keeps the tires flatter on the ground for longer instead of rolling up onto the outside edge and reducing the contact patch.
I wouldn't say that "keeping the tires flatter on the pavement" is the opposite of what a traditional rear sway bar does. An anti-sway bar's main goal is increasing roll-resistance by more solidly connecting the left and right suspension together. When the right side compresses up, the bar transfers the same torque to the other side, pulling up on that side.
Additionally, this has the effect of increasing apparent spring rates while under cornering loads because any forces compressing the suspension on one side are transmitted to the other side via the bar. While going straight, the suspension will usually deflect upwards while together and just the normal spring rate will be in action, not the additive forces via the bar.
Even with the car seemingly oversteering less, ultimate grip is raised and it certainly doesn't understeer any more than normal unless you try to get it to. I'm not sure what the secret formula is for getting the rear end to step out even more than stock but I imagine it might be an increase in rear spring rates without increasing the stiffness of the twist beam rear axle.
Once I have had more time to really push the car at the (new) limits I'll be able to comment on exactly how it behaves. I have driven the car hard through turns on roads I know well and the limit is definitely starting to be higher than I feel safe trying to find on public roads. Until I know how it breaks free when it decides to finally let go I'm not going to try my luck.
Put it this way, there's a particular S curve on a back road that I can normally take at 63 or so (35 limit). Yesterday I drove it at 70 and the car was planted and sure. Not even any tire noise.
Here's a blurb of RTB and additional stiffness: http://www.autospeed.com/cms/article.html?&A=112587
Finally being able to drive my car, I can echo every sentiment ISO has mentioned so far about the rear end. With this new sensation, I can say that before it was installed the rear end could be called sloppy. I didn't even use bushings. Definitely worth the money.
Now the whole with the 6-point brace is a different story. Basically on rails, goes where you point it, sticks to the road and inspires confidence.
Now the whole with the 6-point brace is a different story. Basically on rails, goes where you point it, sticks to the road and inspires confidence.
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