Project GD STI: Getting Rid of Chassis Flex with Cusco


Underneath the car, we used Cusco's lower cross member brace, which stiffens the car's subframe in the area of the lower control arm mounts.

The brace also couples the subframe to the unibody to reduce the flex and shifting in-between them as well.


These Cusco braces shore up the middle of the car's body, bolting to the unibody in several places. They help stiffen the chassis in both bending and torsion.

These smaller braces help couple the car's rear subframe to the unibody. The rear subframe has a tendency to move around by as much as a half an inch under hard side load.

This is a known trouble area on the GD chassis, and our car has some special locking bolts and solid bushings from Whiteline to help pin the subframe in place. You can see this in earlier chapters of this project. These braces will provide some additional stability here and also greatly help stiffness in torsion.  


This brace goes in the rear of our car, ties the two rear frame rails together, and couples them with the rest of the rear unibody in three places.

We were thinking that this brace would make more of a difference in the JDM versions of the GD because of the less substantial bumper brace in the JDM model, but we have seen a video of how much the back of the GD flexes under cornering load so we decided to give these a try. 

Mitsubishi added a such a rear brace to the back of the US market MR model which we have tested and found to be effective. 

Cusco makes an additional rear underbrace which we opted not to use because it has big bends in it and is very small diameter, so we did not feel that it would be too effective and it mostly serves as a mounting point for their rear diffuser. 

They also make a brace for the very front of the car which we didn't use because we were worried about it interfering with our Greddy front mount intercooler.  We will cover our own bracing solution for this part of the car in a future article.


Howard checks to see how the front brace will fit out our car. Our car has a Whiteline anti-lift kit which has some effects on how the bar will install. 


  1. After installing all the Cusco parts do you think that if you could do it over you’d have chosen Cusco instead of Whiteline for the parts you replaced in “Part One- Rebuilding the Suspension” ?
    I’ve looking to do the same suspension things to my 04 STi as you did with with this 05. I’m tempted to be just as snobby as you and go all Cusco. coilovers, bushings, ends, links, bracing, etc.
    Do you think that would be too far and its better that you got KW, Whiteline and Cusco in various parts?

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