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Align It YourselfUnderstanding And Adjusting Front-End Alignment
At first glace, front-end alignment may appear to be a subject for only the most seasoned suspension professionals. However, when you learn the basics of front end alignment, and what your suspension and steering do, it becomes easier to understand and maintain yourself. There's a great confidence that comes from knowing how to keep your car aligned.
Keys To Proper Front-End Alignment
Front-end alignment is nothing more than tire/wheel angle as they relate to the road ahead. You are seeking two things from proper front-end alignment: confident handling and tire wear. In other words, you want alignment to be so good that you and the vehicle become one.
Proper front-end alignment is contingent on how your vehicle is loaded. Most vehicles are aligned empty. However, under ideal circumstances, you have the weight of the driver, fuel, and any contents, which also affects front-end alignment. Older cars and trucks, are based on what was available at the time such as bias-ply tires instead of the updated radial tires. This is where you have to learn what works best with today's tires and road conditions. The way you drive also affects alignment - here's how.
There are three elements associated with front-end alignment: caster, camber, and toe.
Caster, as the word implies in degrees, is like the wheels on a shopping cart or mechanic's creeper. Lets draw an imaginary line from upper ball joint to lower. If you have a kingpin, the imaginary line is the kingpin. The kingpin was used on the front-end of older vehicles and actually still some of the bigger trucks today before ball joints. It's the main pivot point for the spindle that your wheel bolts to instead of ball joints. The wheel/tire is centered between upper and lower ball joints or centered on the kingpin. Depending upon manufacturer, tire/wheel isn't always centered on ball joints or kingpin. It is the angle of the kingpin or ball joints (pivot point) as they relate to the wheel/tire. If the upper ball joint or top of kingpin points to the rear of the vehicle, you have positive caster. If it points to the front of the vehicle, you have negative caster.
When you have positive caster, the steering wheel will want to center because the wheel is trailing the centerline like front casters on a grocery cart. When you have negative caster, steering will be sluggish.
If ever you've been around road or stock car racing, you've probably heard the term "Ackerman Effect", which is when you get toe-out in turns, or, what is simply the difference in steering angle between inside and outside tires in turns. The steering angle of the inside tire is greater than the outside, which is what you want so the front-end can steer you right into the turn with ease.
Cross-caster is where caster is different from side to side for reasons of taming crowned pavement, or to gain a specific type of handling, especially with roundy-round circle track racers. Most of the time caster is the same on both sides.
Camber is tire/wheel angle as it relates to the vehicle and road ahead in degrees. Think of camber like your own anatomy. You're either bow-legged, dead center, or knock-kneed. If you are bow-legged, that's positive camber in degrees where the top of the tire is pointed outward. If you are knock-kneed, that's negative camber in degrees where the top of the tire is pointed inward. Zero camber is 12 and 6-o'clock square with the pavement. You don't want too much camber either way because it can adversely affect tire wear.
Most street applications call for less than a degree of negative camber for good corning where tire contact patch only gets better in turns. Racing applications call for even more negative camber for hard cornering. Camber is adjusted by moving either upper or lower control arm in or out with an eccentric, shims, or serrated mating surfaces that lock into place.
Cross-camber is camber that varies from side to side to work effectively with certain track conditions.
Toe is the distance between tire leading edges, versus tire trailing edges. If leading edge treads are further apart than trailing edges, you have toe-out. If leading edges are closer, you have toe-in. Most applications call for a pinch of toe-in, which allows the steering wheel to smoothly return to center. Toe-in makes the front wheels want to track nice and straight with a snappy return to center. Road race and circle track cars prefer a finite amount of toe-out for a predictable roll into turns.
Toe can be checked and adjusted using a tape measure or toe gauge, with the latter being a Manco piece available from The Eastwood Company. Either way, you measure the distance from tread to tread or sidewall-to-sidewall to determine how much toe you have. You may also use a string of a given length to measure toe.
Marlo's Frame & Alignment - (818) 341-0940 - www.fly-ford.com
Mustangs Etc. - (818) 787-7634 - www.mustangsetc.com
Ramon's Automotive - (661) 274-7900
The Eastwood Company - (800) 343-9353 - www.eastwoodco.com