test-tune-subaru-sti-125-010

SIDEBAR: CIRCUIT SETUP

Our T&T STI may have been going through its performance parts testing in stages, but it has been making the jaunt to the track almost every other weekend since it was purchased second-hand. These frequent track excursions meant that, in addition to being able to test incremental performance improvements, the suspension and chassis components began to reveal their from-the-factory shortcomings.

To help mitigate the problem and allow our STI to reap the benefits of the performance parts adders (by way of faster lap times) we decided to stiffen the chassis. We enlisted the help of GT Spec who provided us with a host of bolt-on chassis stiffeners, allowing us to selectively choose the combination of bars that would offer the most flex-reduction with the least cabin-area intrusion. Among these were a GT Spec fender brace that triangulates the fender and front-door section (below, left) as well as a multi-point strut tower and trunk brace (below, right). These braces help reinforce potential weak spots and flex points along the chassis without significantly reducing driver or passenger comfort, an important
consideration for a street car.

To further help with faster lap times, we set up the STI with a track-capable wheel and tire package consisting of a set of Mach V Motorsports’ Rota D wheels wrapped in Achilles Tire’s new 123S competition tires. The Mach V Motorsports Rota D wheels are available in two different widths, with Subaru-specific hub bore, offsets and bolt patterns in addition to four different finishes. Our Test & Tune STI now rolls on Rota D wheels in a Subaru-specific 18×9.5-inch +40 offset that allows the user to run wider rubber (in the 265 to 275 range) to maximize grip. The Achilles 123S race tire features a rounded tread profile to allow easy transitions between straight-line and high-speed cornering maneuvers but is said to be comfortable enough for daily street-driving.

We’ll further examine the STI’s performance handling capabilities in future editorial installments. Stay tuned.

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