2013 Scion FR-S: Hancha Adjustable Rear Lower Control Arms
July 5, 2013
With the front end camber needs of Project FR-S, our long-term 2013 Scion FR-S, handled, we turned to the rear suspension. It's a multi-link layout back there, so its camber loss with roll is less precipitous than in the front. As such, the rear won't need as much additional negative camber as does the front. But like the front suspension, there's no factory provision to dial in camber in the rear.
To right this wrong, Hancha developed a proprietary adjustable rear lower control arm (LCA) that's made right here in the US.
Hancha first modeled the stock LCA and found that, while lightweight, it was lacking in longitudinal stiffness. Thus, their goal was to create an adjustable LCA that was more robust than stock without being heavier.
The body of the LCA itself is CNC-machined from aluminum and receives an oversized rod end and linkage adjuster that lengthens or shortens the arm in order to provide the necessary camber. According to their analysis, the Hancha LCA reduced mechanical stress by 900% and was 1100% stiffer than the stock arm, all without a weight penalty compared to stock. Proof of their confidence is found in the company's three-year warranty that includes motorsports use. Race parts with warranties are rare beasts.
Pictured above are the QA1 rod ends and linkage adjusters that normally ship with the Hancha LCAs. They're beefy 3/4-inch aluminum, and the rod ends have a Nylon/PTFE race that is self-sealing and self-lubricating. They are, by design, not proprietary items so in the event replacements are needed they can be found with relative ease.
In our case, due to a shipping snafu at the last minute, the linkage adjusters and rod ends would need to be sourced locally. We were operating with only hours before departure to Laguna Seca, so Hancha scrambled some steel rod ends for us.
Linkage adjusters, however, were proving elusive.
And then, John at Specialty Cars totally saved the day. "Jay, I'll just make them!" he said cheerily after chasing several leads that led to dead ends. In the space of a few hours, he located the necessary raw materials and fabricated the linkage adjusters from scratch. Then he dropped them off at my house. Talk about service!
Take a look at John's handiwork above. They fit perfectly. I think I'll be enlisting his services for other projects too...
The rod ends in the Hancha LCAs also eliminate a source of squishy rubber found in the OEM arms. This will enhance precision at the price of some additional NVH, a tradeoff we're willing to live with. Likewise, when loaded up in a corner, the rod end will not deflect as much as the rubber bushing. The LCA is oriented aft of the rear axle line in the FR-S, meaning that during hard cornering there will be a touch less loss of toe-in with the Hancha arms compared to stock.
Once I finished installation of the arms, I gave the FR-S an eyeball alignment and then set off to Stokes Tire Pros for a real alignment. There, they dialed it in to my specs. In the front we achieved -1.9 degrees camber and zero toe; the rear was -1.7 degrees camber and zero to 1/16" total toe-in.
It all came together with minutes to spare prior to our scheduled departure time for Mazda Raceway Laguna Seca.
Jason Kavanagh, Engineering Editor