The Ford Focus ST is an amazing handling machine, being incredibly unique amongst front drivers for its ability to rotate the rear end. More than just chassis tuning, however, the Focus ST has a secret.
Well known for using what the company calls Torque Vectoring Control on the front axle, pitch the ST into a corner and its rear-end swings around by another means.
We recently tested the Focus ST on the track for an upcoming comparison article with the Mazdaspeed3 and AutoGuide hot shoe David Pratte had his suspicions, which have since been confirmed by Ford’s chassis guru at Team RS Vehicle Dynamics (and a man with a rather similar name) David Put.
“I will not tell all the goodies,” says Put about Ford’s handling secrets, “but you’re absolutely right.”
What Put is referring to is the sensation we experienced; that the Focus ST rotates its rear-end by braking the inside rear wheel in a corner.
When the ST debuted Ford boasted about its Torque Vectoring Control system that can add brakes to the inside front wheel. Rather than a heavy or complex limited slip differential that distributes more power to the outside wheel and less power to the inside wheel to help maximize vehicle grip (and, therefore, speed), TVC simply reduces the amount of power making it to the inside wheel by adding brake.
That happens too says Put, commenting that the car’s computer knows to brake the inside front wheel to help the vehicle rotate. In fact, the front does 95 percent of the work, he says, though that extra five percent braking in the rear is Ford’s secret sauce.
This trick helps create oversteer (a trait commonly associated with rear-wheel drive cars), while also reducing understeer – a performance robbing trait of front-wheel drive cars.
SEE ALSO: Ford Focus ST Review – Video
Still, Put insists that, “the base chassis is still responsible for the most part of it [the car's handling dynamics],” commenting that, “Even with best control system you still need to do most work on classic chassis tuning.”
The reason for this handling magic is more than just for performance, though that’s the basis behind it. The Focus ST, “had to be a very day to day useable car,” says Put, hinting that other methods for making the Focus ST tail-happy through thick rear swaybars and a stiff rear suspension were out of the question, as they would not only ruin the ride quality, but could also make the car too lively for anyone but a race car driver to control.
“You gotta have your fun,” says Put. “We believe fun is when you can also put a car in a smooth drift when you want to, even in front wheel drive cars.”
That, they have achieved through innovative braking in the Focus ST.
But there’s more. Put confirmed that the outside rear wheel brake may also be engaged to help stabilize the car in a drift, rather than have it rotate completely around.
He also emphasized the fact that turning Electronic Stability Control (ESC) off means full-off – a feature exclusive to the brand’s ST and RS models. How that’s possible when all four brakes are working to control the car’s trajectory does, however, seem contradictory.