M13 Chapter 9: Four-Wheel Alignment, Part 1 Primary Angles

In general, a vehicle may exhibit a drift if the cross caster difference is of between _________ degrees and a pull if the cross caster difference is greater than ______ toward the side with the least positive caster. Rear caster is not measured.

0.5 and 1.0, 1 degree

Negative caster

Is the angle of a line through the center of the tire that is tilted forward in relation to the true vertical centerline of the tire viewed from the side.

Positive caster

Is the angle of a line through the center of the tire that is tilted rearward in relation to the true vertical centerline of the tire viewed from the side.

Negative camber

Occurs when the camber line through the center of the tire is tilted inward in relation to the true vertical centerline of the tire viewed from the front of the vehicle.

Positive camber

Occurs when the camber line through the centerline of the tire is tilted outward in relation to the true vertical tire centerline viewed from the front.

While on a short-and-long arm suspension system, the caster line intersects the center of the upper and lower ball joints (Figure 9-18). Positive caster occurs when the caster line is tilted _____ toward the ______ of the vehicle in relation to the vertical centerline of the spindle and wheel viewed from the side (Figure 9-19). Negative caster occurs when the caster centerline is tilted _______ the ________of the vehicle in relation to the spindle and wheel vertical centerline.

backward, rear, toward, front

A reference line begins at the ______ (ground) _____ of the tire and wheel and extends upward at a ______ degree angle to the road.

base center, 90

The camber may be adjusted with the cam on the upper strut-to-steering knuckle bolt on some MacPherson strut front suspension systems. Negative and positive _________ are the same on a short-and-long arm front suspension system as they are on a MacPherson strut suspension system (Figure 9-7).

camber angles

When the front wheels are adjusted to the manufacturer's specified camber setting, the front wheels will remain at, or very close to, the 0 degree ____________ during average driving conditions. Therefore, maximum tire tread life and directional stability are maintained.

camber position

This left side to right side difference is referred to as _________ and is shown on the alignment computer's readings screen (Figure 9-3). Some manufactures specify a maximum allowable amount of cross camber.

cross camber

Other manufactures do not specify an acceptable amount and the general assumption as stated above is that a vehicle may exhibit a drift if the __________ difference is between 0.5 and .75 and a pull if the cross camber difference is greater than toward the side with the _________ camber reading. Rear camber differences do not cause vehicles to pull or drift but do cause ______ just as errors in the front.

cross camber, higher, tire wear

Caster is measured in ______ and positive caster is specified on consumer production vehicles. Cross caster is the difference in caster between the ____________ of the vehicle (Figure 9-20)

degrees, right and left side

When the camber on the front wheels is adjusted to the manufacturer's specifications, vehicle __________ is maintained. If the camber adjustment on the left front wheel is used to offset road crown, the caster on both _______ must be the same (Figure 9-16).

directional stability, front wheels

Like camber the caster tolerance is a means provided by the manufacture to fine tune the suspension system to specific __________. Many vehicles today do not allow for a change in the _______ as part of a wheel alignment. But this angle should always be measured as part of a ________ and if out of tolerance, the root cause should be determined and appropriate repairs should be recommended to the customer.

driving habits, caster angle, wheel alignment,

Any force exerted on the pivot causes the wheel to turn until it is lined up with the _________ on the pivot, because the weight on the wheel results in resistance to __________ (Figure 9-23).

force, wheel movement

Front cradle position is extremely important to provide proper _____________ on a front-wheel-drive vehicle. For example, if the vehicle is involved in a side collision and most of the collision force is supplied to the front wheel and chassis, the cradle may be pushed _________. On the side of the vehicle impacted during the collision, the front suspension and cradle may be pushed _______, and the other side of the cradle may be forced outward.

front wheel camber, sideways, inward,

Caster is not considered a direct tire wear angle but is a directional stability angle and is used to __________________ returnability.

improve cornering and steering wheel

A camber specification and tolerance is specified by the vehicle manufacture for both the front and rear (Figure 9-6). The specification is the preferred angle and the tolerance is the permitted amount that can be __________ (+) or ________ (−) from the preferred angle. The tolerance is a means provided by the manufacturer to fine tune the suspension system to specific ___________. It also allows for some change and wear that may naturally occur between alignments without a noticeable impact on directional stability or excessive tire wear.

increased, decreased, driving habits

During an alignment, camber is considered a live measurement because the computer is continually updating the sensor ___________ on the computer measurement screen. Some alignment machines will allow you to adjust __________ with the weight on or off the _______ using a program designed to allow the vehicle to be lifted. Hunter Engineering calls this program "Jack-Up Selected Axle."

information, camber, wheels

Camber is defined as the ___________ tilt of the tire and wheel assembly as viewed from the front of the vehicle (Figure 9-1).

inward or outward

Excessive negative camber tilts the wheel _________ and concentrates the vehicle weight on the _______ of the tire. This condition causes wear and scuffing on the inside edge of the _________ (Figure 9-13). Therefore, correct camber adjustment is extremely important to providing normal tire tread life.

inward, inside edge, tire tread

Camber can also cause smooth, tapered tire wear to either the ____________ edge of the tire tread around the entire tire's circumference and is typically isolated to the _________ area of the tire (Figure 9-4).

outer or inner, tread shoulder

Positive camber is obtained when the top of the tire and wheel is tilted ________, away from the true vertical line of the wheel assembly. Negative camber occurs when the tire and wheel centerline tilts ________ in relation to the wheel assembly true vertical centerline. The camber angle is measured and referred to the same for both the front and rear tires, meaning negative camber is the inward tilt of the tire at the top whether it is in the ___________of the vehicle.

outward, inward, front or rear

On most modern suspension systems during wheel jounce, the top of the wheel moves _______ and creates a more _______ camber angle (Figure 9-8). During wheel rebound, it is desirable to have very little camber change to minimize _____ wear. A short-and-long arm front suspension system will have a slightly negative camber during __________ travel (Figure 9-9).

outward, positive, tire tread, wheel rebound

If a front wheel has excessive positive camber, the wheel is tilted ________ and the vehicle _________ is concentrated on the outside edge of the tire. Under this condition, the outside edge of the tire has a smaller ___________than the inside tire edge.

outward, weight, diameter

When viewed from the side, caster is the angle formed when a line is drawn through the upper and lower ___________ in reference to true _______. On a MacPherson strut suspension system, the caster line intersects the center of the upper _______ and lower ball joint (Figure 9-17).

pivot points, vertical, strut mount,

If a piece of furniture mounted on casters is pushed, the casters turn on their ______ to bring the _________ into line with the pushing force applied to the furniture. Therefore, the furniture moves easily in a straight line (Figure 9-22).

pivots, wheels

Too much _________ will cause outside edge wear to the tire shoulder (Figure 9-5). Too much __________ will cause inside edge wear to the tire shoulder.

positive camber, negative camber

If one front wheel has more __________ than the other front wheel, the steering pulls toward the side with the least amount of ____________.

positive caster,

When the front suspension and cradle are moved inward, the camber on that side of the vehicle becomes more ______. When the cradle, suspension, and bottom of the wheel on the opposite side are moved outward, the camber is moved toward a _______position. Often this is noted as an equal and opposite difference in side-to-side camber.

positive, negative

Simultaneously, the camber on the outside wheel moves to a slightly more _______ position. This action on the outside wheel causes the outside edge of the tire to grip the __________, which helps prevent sideways skidding (Figure 9-11). Frequent, hard, high-speed cornering causes wear on the edges of the _______.

positive, road surface, tire treads.

When this action occurs, the camber on the inside wheel becomes less _________ and the inside edge of the tire grips the road surface to help prevent _________ (Figure 9-10).

positive, sideways skidding

The caster specification and tolerance is specified by the vehicle manufacturer for the front wheels (Figure 9-21). The specification is the _________ and the tolerance is the permitted amount that can be ___________ (+) or __________ (−) from the preferred angle.

preferred angle, increased, decreased

If the side-to-side difference in front camber is greater than 0.5 to 0.75, the vehicle may exhibit a _________ to the most _______ side (Figure 9-2) as a general rule.

pull or drift, positive

Some car manufacturers use the ________ of camber to offset this pull to the right caused by road crown. In these vehicles, the left front wheel may have 1/4 to 1/2 more _________ than the right front wheel.

pulling effect, positive camber

Therefore, the outside tire edge has to complete more ________to travel the same distance as the inside tire edge. Because both edges are on the same tire, the outside edge must ________ on the road surface as the tire and wheel revolve (Figure 9-12).

revolutions, slip and scuff

During hard cornering at high speeds, centrifugal force attempts to move the vehicle __________ to the outside of the turn. Under this condition, more vehicle weight is transferred to the side of the vehicle on the _________ of the curve. Therefore, the front suspension on the outside of the curve is forced _______, whereas the front suspension on the inside of the curve is lifted _______.

sideways, outside, downward, upward

When camber angles are equal on both front wheels, the camber _________ are equal, and the vehicle tends to maintain a __________ position. If the camber on the front wheels is significantly unequal, the vehicle will drift to the side with the greatest degree of ___________.

steering forces, straight-line, positive camber.

Put another way, camber refers to the ________ of a line through the tire and wheel centerline in relation to the true __________ of the tire and wheel.

tilt, vertical centerline

A wheel that is _______ tends to steer in the direction it is ______ (Figure 9-14). For example, a bicycle rider tilts the bicycle in the direction he or she wishes to turn, making the turning process easier.

tilted

Camber angle is displayed in degrees on an alignment computer. Camber is an angle that can affect both _________and_________, such as a pull or drift.

tire wear, directional stability

Crowned highway design prevents _______ buildup on the driving surface. When a vehicle is driven on a crowned road, it is actually driven on a slight _________, which causes the vehicle steering to pull toward the _______ (Figure 9-15).

water, slope, right