Dempsey's Tire Center

Tag: castor

Wheel Alignment – Castor

by on Jul.23, 2009, under Alignment

Wheel Alignment Defined
By Matthew Wright, About.com

Wheel alignment is important to the health of your car or truck. If you hit a massive pothole, you might bump your suspension out of the carefully calculated locations that the components have been set. All of the elements that make your car go straight are called “alignment.” Some shops try to make it seem like rocket science, but wheel alignment is a fairly straightforward affair. The inclusive term “wheel alignment” involves three main measurements — caster, camber, and toe. These measurements have standards that a technician uses as targets of adjustment. In other words, get as close as you can to the right measurement.

The good news is that most modern cars only have adjustments for toe. Caster and camber went the way of the dodo thanks to the McPherson strut.
casterCaster is the tilting of the uppermost point of the steering axis either forward or backward (when viewed from the side of the vehicle). A backward tilt is positive (+) and a forward tilt is negative (-). Caster influences directional control of the steering but does not affect the tire wear and is not adjustable on this vehicle.

Caster is affected by the vehicle height, therefore it is important to keep the body at its designed height. Overloading the vehicle or a weak or sagging rear spring will affect caster. When the rear of the vehicle is lower than its designated trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than its designated trim height, the front suspension moves to a less positive caster. With too little positive caster, steering may be touchy at high speed and wheel returnability may be diminished when coming out of a turn. If one wheel has more positive caster than the other, that wheel will pull toward the center of the vehicle. This condition will cause the vehicle to pull or lead to the side with the least amount of positive caster.

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