Project GR STI- Generation 3, an Introduction


Project STI dash 

Front Suspension
The front suspension on the previous generation STI had some traits that we did not like.  The GD was afflicted with steering that had a numb on center feel and a poor return to center when cornering.  High powered modded STI’s had some hints of torque steer and a large amount of anti dive/lift geometry in the front suspension lead to torque bind and a non linear build up of understeer when trail braking and on the throttle at corner exit.  Thus, the STI had a vastly less crisp turn in feel and response when compared to its arch rival, the EVO.

The good news is that the Subaru engineers have been working on the suspension to improve all of these issues.  At a glance the front suspension on the GR appears to be identical to the GB but there have been numerous subtle changes in the front end’s geometry.  The amusing thing is that all of the changes that Subaru has adopted for the new car are all popular things that some of the top Subaru tuners (mainly Whiteline) did to improve the GD.

GR STI front suspension

The GR front suspension is basically the same as the GD, a simple McPherson strut with some basic geometry improvements, less anti dive, more kingpin inclination and more caster. It also looks like Subaru is trying to lighten things up and the new car looks more wimpy here than the old one.

The front suspension is of the tried and true to the point of being yawnable, McPherson strut design.  We wish that the new multilink rear suspension found its way to the front but realistically, any multilink will be difficult to package due to the width of the wide boxer motor. The most notable things about the new suspension’s geometry is more positive caster and a greater steering axis inclination angle.  Both of these geometric changes increase straight line stability, on center feel and steering return to center.  Increasing positive caster also improves turn in and contributes to negative camber gain as the steering wheel is turned off center.  In addition to improving on center feel and straight line stability, increasing the steering axis inclination angle moves the Dave point closer to the front tires contact patch center, reducing tendencies for torque steer and steering pull when accelerating or braking on split coefficient of adhesion surfaces.

GD STI front suspension
Doesn’t the older car look stronger and more rigid? We know looks can be deceiving but the old car looks like it shows its WRC rally proven heritage.

The GR has less anti lift/anti dive incorporated into the front suspension geometry than the GD as the front lower control arm is more on plane with the ground than the older car.  This would be a cue straight from Whiteline as they sell a popular kit for the GD that does just this by relocating the rear pivot of the lower control arm, reducing anti and increasing positive caster at the same time.
Although we don’t have any real data, it seems like the front suspension is less rigid than the old car.  The GD had a deep section perimeter subframe but the GR has stuff that just looks weaker and less tied together.

GR STI seatsProject STI dash

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