The camber angle refers to the inward or outward tilt of the tire when viewed from the front or rear of the vehicle. Negative camber exists when the top of the tire leans inward. If the top of the tire leans outward, positive camber exists. If the tire is positioned at a true vertical, it's set at zero-camber. Camber angles are measured in degrees. The camber angle is adjusted to maximize tire wear, handling and directional stability. Most cars have factory specifications for slightly positive camber. This is done to reduce steering effort, to increase highway-speed directional control.
It's common for performance drivers and road-course competition drivers to request a negative camber at the front wheels, in order to maximize tire tread contact in severe turns. Though the front wheels may be set in a severe -- say, three degree -- negative camber and tire tread contact may be diminished when the vehicle travels straight (chances are, the inner tread only will actually contact the road), when the vehicle enters a hard right hand turn, the tire tries to flex and 'roll-over.' The result is full-tread contact of the left front tire during the turn. Keep in mind that this is primarily true only in dry road conditions. In severe wet-surface conditions, there may not be sufficient tire grip to generate enough rollover to obtain a full-width tread contact patch. In that case, a camber setting closer to zero would likely perform better.
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Looking at a wheel from the side of the car, the caster refers to the position of the wheel in relation to the strut centerline. When the top of the strut is moved back this is called a positive caster angle. All vehicles use a positive caster angle. Typically, caster settings will be from + ½ degree to + 4 degrees. Higher caster settings give a little more straight-line stability, while lower settings make the steering lighter and the car tend to turn easier.
The best way to comprehend the effects of caster is to think of a bicycle. The handle bars are typically always behind the front wheel, a positive caster angle. The further back the steering input is, the more stable the bicycle. On a unicycle, where the steering input is directly on top of the wheel, the steering is erratic and not as easily controlled. It is also easily effected by bumps and road surface deviance's. Caster settings on many vehicles, like Neons, are fixed and cannot be adjusted without aftermarket plates. |
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Toe is measured in inches and refers to the in or out turn of the wheels from a straight-ahead position. Look down at your feet and picture them as your tires on the car. Now, move your toes toward each other or "pigeon toed" -- this is "toe-in". Most vehicles have specifications for slight "toe in"; the front of the wheels were turned slightly inwards. A slight toe-in increases steering stability and response, and as vehicle speed increased, the tire resistance would cause the toe to change to the straight-ahead position. |
