Positive caster positions the lower ball joint in front of the upper ball joint or strut mount. This results in the tire contact patch hitting ground in front of the steering system and suspension components. The origins and numerous documented benefits of positive caster date all the way back to the late nineteenth century.
Discoveries of the French automotive engineering pioneer Arthur Constantin Krebs, for all you history buffs out there. Positive caster creates two primary benefits:. And without positive caster and the resulting self-aligning torque, the vehicle would be very inclined to wander at highway speeds.
For a risk-free preview, send a shopping cart, which has negative caster at the front wheels, on its way. Specifically, positive caster helps to create increased negative camber on the outside wheel during cornering.
In performance driving circles a caster increase — sometimes to the maximum available setting that the vehicle will accommodate — is credited with improvements in vehicle handling, maximum traction, and steering responsiveness. Negative caster positions the lower ball joint behind rearward of the upper ball joint or strut mount.
Unlike in a positive caster arrangement, the wheel and tire contact patch hit the ground behind the steering system and suspension components. The self-aligning torque and straight-line stability that is characteristic of positive caster are absent in a negative caster setting.
Caster settings are not a primary, direct factor in tire wear. However, excessive positive caster in association with other alignment maladjustments can exacerbate a tire wear issue. For example, a tire wear pattern called feathering can result from a combination of too much caster with incorrect toe settings.
Tire feathering is characterized by a high-low, smooth-sharp variation in the wear pattern of the tread blocks. Of all of the alignment settings, however, caster is the least likely to be a cause of uneven or abnormal tire wear. Arthur Krebs and his positive caster concept! By continuing to use our site, you consent to the placement of cookies on your browser. Caster affects the steering ease and the stability of the vehicle in a straight line.
A car that pulls to one side when traveling in a straight line may have negative caster. Cars with power steering should have positive caster, so this vehicle should have its suspension checked and realigned by a mechanic. Camber is another angular measurement in the suspension, measuring a different axis of tilt than caster.
This affects the area of the tire contacting the ground during various driving maneuvers. Positive caster is when the lower pivot point is located in front of the upper pivot point when viewing the vehicle from the side. This causes heavier steering, or greater difficulty in turning the steering wheel only noticeable in vehicles without power steering. Modern cars can easily maximize the benefits of positive caster because they have power steering and are not affected by the heavier steering.
Self aligning torque happens when the lower pivot point is farther forward than the upper pivot point and the force is then applied to the front wheels to make the wheels want to return to their neutral position in a turn. This is the ideal range to maximize straight line stability and still allow for comfortable turning. Positive caster increases negative camber when the wheels are turned due to the geometry of the suspension components.
This is good for cornering as it maximizes the area of tire that is in contact with the ground on the outside front wheel, which is under the most load during the turn.
Bicycles have positive caster, since the front wheel steering axis is angled forward to give the rider more stability in a straight line. Related: Symptoms of a Bad Wheel Alignment. Positive and negative caster mainly apply to race cars, and unless your vehicle is lifted or customized in some way that calls for an adjustment, street cars usually run on factory determined settings. The amount of toe, whether it's toe-in or toe-out, is expressed as the difference between the track widths as they are measured at the leading and trailing edges of the tires.
Toe is expressed in degrees or fractions of an inch, and while your wheels should be pointed directly ahead as you are traveling straight forward, there are some benefits to toeing depending on the type of vehicle that you drive. The purpose of toe is to ensure that all four wheels roll parallel to one another. However, race cars use toe-out to promote enhanced turning ability.
Street cars, or basic passenger cars, use toe-in because there is no need to corner quickly. Toe-in also provides increased stability because it discourages turning. If your vehicle has the proper amount of toe you should experience ideal straight line stability, corner entry, and very little tire wear. Toggle navigation. What is Camber? Positive Camber - When your wheels are tilted outward, the vehicle has improved stability.
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