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| The front lower control arm is pretty close to parallel to the ground which means there is very little anti dive in the front suspension geometry. We like this in a sports car because it means that the effective wheel rate won't rise too much in the front suspension under trail braking which means better turn in while trail braking. Most race cars have very little anti dive in their front geometry but most production cars do. The reason why is so that dive can be controlled with soft street car springs and most OEM's feel that understeer is best anyway. We think that the FR-S can get away with little anti dive because the CG is so low on this car. Another interesting point is that the front strut is mounted unusually inboard so the front suspension motion ratio is pretty high. This means that a pretty stiff front spring will be needed. |
Now this is a very early car and some specs might change before actual production but it is probably safe to say that this is a 95% accurate example of a production car. You have to excuse our impromptu photography. We just happened to have a camera, it was very dark and we did not have lighting equipment or tripods so it's not pretty but that is not the point, we want to give you some insight on the car's underpinnings, what its potential is and how it will probably work.
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| For drift fans, it looks like the spindle can easily be modded for more steering angle while keeping a reasonably decent amount of overall bumpsteer and Ackerman. After replacing the tie rod ends with spherical bearings, the spindle can simply be faced, redrilled and reinforced to move the tie rod location inward. |
The car’s front suspension is a very conventional MacPherson strut design. The geometry looks to be good with decent amounts of caster, trail and king pin inclination for a fairly low scrub radius. To the driver this means good self steer, straight line stability and good turn in. The strut is mounted pretty far inboard so the suspension motion ratio is going to be pretty high for a strut which means a relatively stiff spring will be needed. This part of the suspension geometry is pretty reminiscent of the Nissan S chassis which we consider to be a very good execution of a MacPherson strut.
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| The tie rod inner pivot is inboard of the lower control arm pivot and at a flatter angle, this will cause toe in under suspension compression. The front sway bar is pretty tiny but it has a small moment arm so its effective stiffness is probably higher than it looks. |
One thing we noticed is that the car has a fairly low roll center and if the car is lowered much at all the lower control arms will point upward with the roll center quickly ending up below ground. This will do two things that are not so great; the car will have a large roll couple and a strong tendency to roll which must be countered with stiff springs and/or swaybar. However the FR-S does have a very low center of gravity due to the low slung boxer engine so perhaps this may still be tolerable.
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| Hey look at this, the front of the lower control arm has this rubber bushing with a cutout for compliance under load in the cornering direction. This probably helps reduce road shock. Since the front of the control arm will now move more in relation to the rear part of the arm and the tie rod, compression under load will result in toe out under load. Perhaps this subtlety counters the toe in under roll that the tie rod location produces as well as lowering NVH and shock? Something clever might be going on here. |
Next due to the angularity of the lower arm when lowered, the front suspension will lose negative camber under roll which will reduce grip and even lead to understeer in a low car unless a lot of static negative camber is dialed in or roll is greatly reduced with stiff suspension. Big negative camber hurts braking traction and causes the car to be road crown sensitive and tramline on cracks and grooves. Being too stiff hurts mechanical grip. Whiteline if you are reading this, this car really needs your long shank ball joints and tie rod ends to correct the roll center. Make some right away please. Maybe your Subaru kit might fit. The best solution before the aftermarket responds might be to not lower the car more than 1.5” or so.
