Part 2: Four More Steps To Better Handling
In part one of this series (SCC, June '05) you learned four basic steps to improving your car's handling. Those steps were easy. They involved the use of basic performance suspension parts available for most cars and, no doubt, many of you have already taken those steps. This month we explore more advanced suspension tuning through alignment, chassis stiffness and suspension geometry.
Step Five: Add Negative Camber
For a tire to grip well, it must use all of its contact patch. Thanks to problems like tire distortion and compromised suspension geometry, this rarely happens. When a tire is subjected to side load, its sidewalls flex, digging the outside tread into the ground and lifting the inside.
If you drive hard, you've probably noticed the outside edge of your tires gets chewed up much faster than the rest of the tread. That means the tire isn't using all of its contact patch effectively.
As a car rolls in a corner, the chassis rolls the tire onto its outside edge, making the problem worse. Keeping the tires flat on the road is the primary reason to reduce roll. In part one we listed several ways to do this; the easiest ways are to increase spring rate or use larger anti-roll bars.
The primary tool, however, used for combating tread lift is to dial in more negative camber. Camber is the inward or outward tilt of the tires when looking at them from the front. If the top of the tire leans outward, camber is positive. If the top of the tire leans inward, camber is negative.
Dialing in negative camber helps combat tread lift and wheel tilt. The trick is to add just enough negative camber so the tread stays flat and 100 percent engaged with the ground under side load and roll. But, adding too much negative camber will hurt more than it helps. Too much negative camber will:
1. Reduce braking traction
2. Reduce acceleration traction if it's applied on the drive wheels
3. Increase the tendency to follow cracks and grooves in the pavement
4. Increase wandering caused by road crown
5. Affect tire wear; the insides of the tire tread will wear faster with more negative camber if you don't corner hard. Conversely, if you constantly corner hard, your tires will wear more evenly and last longer