Drift Tengoku — September 2004 · Page 46

During a corner the outer suspension compresses and the inner side tries to rise as the body rolls. The inner suspension needs to extend to follow the road. Insufficient extension can lift the tire and reduce contact.

Helper springs offer a straightforward improvement by adding extension travel, especially useful when exiting slow corners. On a stationary car, less negative camber increases contact, but cornering roll means the answer is not simply to stand the tires upright. The best camber depends on how freely the suspension moves; compression depends on bump in.

With little extension travel, reducing negative camber may work better...

Multi link suspension geometry has a point where deep compression causes toe and camber to change sharply. I call it the point where the motion 'bends.' Such a sudden alignment change can make grip fall away and the rear slide, particularly because toe changes strongly. Reaching it in the middle of normal travel can make the car hard to drive, so settings usually avoid it.

Recently, however, powerful D1 cars have begun deliberately reaching it sooner to exploit that slide initiation point. If a powerful car retains rear grip too long, its eventual breakaway becomes abrupt...

...and difficult to control. Letting the tail step out sooner makes a powerful car easier to manage. That is another reason I lower the rear: to reach the transition point earlier and initiate quickly. The HKS car may share that aim. I have not collected detailed measurements of exactly where the transition occurs or how large the change is, but lowering the rear brings it sooner.

Shortening the traction arm makes the rear tire move forward as the suspension compresses, helping load transfer to the rear. It also draws the wheel toward toe in and negative camber. The deeper it compresses, the more both increase: bump in changes more abruptly than standard. The resulting toe in improves stability and makes it easier to apply throttle.