A Tech Look Under the Scion FR-S!
By Mike Kojima
Recently the Scion FR-S or Toyota 86/Subaru BRZ has been officially unveiled to the motoring public. Most of the stuff about the car on the web has been pretty pictures and cool videos of Ken Gushi sliding around in the rain. Now that the first close to production Scion FR-S’s have been officially rolled out and press embargos have been lifted we will give you a technical look at the car's underpinnings with some engineering commentary.
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| The FR-S suspension is conventional MacPherson strut. The Greddy car had a prototype set of Greddy coilovers. The only adjustment in the front alignment is the toe which is typical. No provision for camber or caster adjustment is present on the stock car, at least this stock prototype! The front suspension has a good amount of caster, king pin inclination and trail which is good for camber gain under cornering, straight line stability, good on center feel and good self aligning torque with minimal scrub. These aspects of the front end geometry are reminiscent of the Nissan S Chassis and older BMW's, good things. |
You are probably dying to know more about the chassis and suspension. Is the car the real deal or is it marketeering hype riding on the DNA of the old AE86. Is it or isn’t it? Well let’s go and take a look. The car we got to see carefully is the black street car built by Greddy which was on display at the official Scion reveal a few weeks ago.
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| The prototype coilovers may have little droop travel as the car was not lowered much but the position of the lower control arm and ball joint indicated a pretty low front roll center, at least with these particular coilovers. The front control arm was perpendicular to the ground under full droop. This means that the roll center when plotted will most likely be under ground . Implications of this are a high roll couple and lack of negative camber gain under roll. This means that the car will need stiff front springs and or anti sway bars and a lot of static negative camber when lowered or the car will tend to lose front grip at the limit, at least when lowered significantly. A lowered FR-S is going to benefit from extended stud ball joints and tie rod ends like those that Whiteline sells for the EVO and WRX. |
At the event our freelancer John N. Frink and Annie Sam got a fleeting view of the undersides of the car and managed to snap a few pictures. A few days later we managed to look at the underneath of the Greddy car while picking up some stuff for Project EVO X. Since the car is no longer a secret and the specs have been released, the nice folks at Greddy let us take some pictures of the underside.
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| The tie rod is out of plane from the lower control am and the inner tie rod joint is out of line from the pivot. It looks like the FR-S will toe in under dive and roll which is good for stability but not necessarily the best for steering response. The Nissan S chassis for instance has a close to ideal steering rack and tie rod location for little bump steer. The FR-S's location is more indicative of stability under braking. |
