Wheel Alignment Checking and Adjustment
Wheel Alignment Checking and Adjustment
The alignment for suspension and steering linkage is usually checked and adjusted if, GO abnormal tyre were exists,
(ii) the automobile handling is felt improper,
(Hi) the suspension has been repaired, or
(iv) a normal preventive maintenance check becomes necessary.
In the past the wheel alignment was measured using a trammel gauge, but nowadays either an optical or an electronic gauge is used. Before tracking the wheels, the following preliminaries should be undertaken.
(a) The tyre pressures are checked.
(b) The correct load on the vehicle is ensured.
(c) The wheels are positioned in the straight ahead position.
(d) The vehicle is moved forward to settle the steering.
(e) The run-out (buckle) of the wheel in checked and the maximum run-out is positioned so that it does not affect the alignment measurement.
Prior to aligning the front suspension and steering systems, the factors to be ascertained that the suspension pivots and ball joints are in good condition, the spring height is correct, the shock absorbers are in good condition, and the tyres are inflated to the correct pressure. Tyres should be inspected for any specific problems. Tyre wear on one side of the tread generally is due to improper camber on the wheel. Smooth tyre wear on both sides of both front tyres indicates excessive slippage when negotiatimg corners at high speeds. Wear on the edges of one tyre normally is due to under-inflation of that tyre and wear on centre portion of the tyre tread is due to over-inflection.
The status of wheel alignment can also be ascertained by observing the wafer edge of rubber left on the side of the tread pattern (Fig. 27.20). The position of the feather is examined to provide an indication of the fault. Feather edge indicates improper toe and copping around the tyre edge, which may be caused by under-inflation or by suspension mechanical irregularities. A wafer of rubber on the inside of the tread recognises that the wheels are toe-in and vice versa. This type of feathering of the tread is often more prominent on one tyre than the other.
Both portable and stationary alignment machines are available. Alignment racks or wheels stands are either above the floor or extended over a pit in which the mechanic can Work comfortably. The alignment rack must be level to compare the alignment angles with the vertical lines. Turntables are located under the front tyres so that the wheels can be turned left or right. Alignment gauges to sense a vertical position are usually a bubble level or a swing weight. Instrument heads are mounted to the front wheels or to the spindle through adapters. Both the front wheels turn towards the near-side due to the combination of road camber and the action of the tyre's self-righting torque. This movement affects the steering geometry and justifies "'hy
(ii) the automobile handling is felt improper,
(Hi) the suspension has been repaired, or
(iv) a normal preventive maintenance check becomes necessary.
In the past the wheel alignment was measured using a trammel gauge, but nowadays either an optical or an electronic gauge is used. Before tracking the wheels, the following preliminaries should be undertaken.
(a) The tyre pressures are checked.
(b) The correct load on the vehicle is ensured.
(c) The wheels are positioned in the straight ahead position.
(d) The vehicle is moved forward to settle the steering.
(e) The run-out (buckle) of the wheel in checked and the maximum run-out is positioned so that it does not affect the alignment measurement.
Prior to aligning the front suspension and steering systems, the factors to be ascertained that the suspension pivots and ball joints are in good condition, the spring height is correct, the shock absorbers are in good condition, and the tyres are inflated to the correct pressure. Tyres should be inspected for any specific problems. Tyre wear on one side of the tread generally is due to improper camber on the wheel. Smooth tyre wear on both sides of both front tyres indicates excessive slippage when negotiatimg corners at high speeds. Wear on the edges of one tyre normally is due to under-inflation of that tyre and wear on centre portion of the tyre tread is due to over-inflection.
The status of wheel alignment can also be ascertained by observing the wafer edge of rubber left on the side of the tread pattern (Fig. 27.20). The position of the feather is examined to provide an indication of the fault. Feather edge indicates improper toe and copping around the tyre edge, which may be caused by under-inflation or by suspension mechanical irregularities. A wafer of rubber on the inside of the tread recognises that the wheels are toe-in and vice versa. This type of feathering of the tread is often more prominent on one tyre than the other.
Both portable and stationary alignment machines are available. Alignment racks or wheels stands are either above the floor or extended over a pit in which the mechanic can Work comfortably. The alignment rack must be level to compare the alignment angles with the vertical lines. Turntables are located under the front tyres so that the wheels can be turned left or right. Alignment gauges to sense a vertical position are usually a bubble level or a swing weight. Instrument heads are mounted to the front wheels or to the spindle through adapters. Both the front wheels turn towards the near-side due to the combination of road camber and the action of the tyre's self-righting torque. This movement affects the steering geometry and justifies "'hy
Fig. 27.20. Section through tyre treads.
a manufacturer recommends a toe setting which appears to contradict basic theory. Due to interaction between the various geometries of a modern vehicle it becomes difficult to pinpoint the cause of a fault from a given symptom. Therefore, a front-end check covering all aspects of geometry is recommended after completing the preliminaries.
Once the instrument head is levelled the camber is read directly from the instrument head or screen. Castor is measured as it affects camber during a turn. Castor is read on a special scale which converts the camber change into a castor. When the wheel is turned from 20 degrees inward to 20 degrees outward with the brake applied, the change in camber indicates castor. If castor is zero, no change in camber is observed as the wheels are turned. Camber change increases with increase of castor as the wheel turns 40 degrees. Steering axis inclination is also measured in a manner similar to castor. But, this measurement includes a change in castor during the 40 degrees wheel turn instead of camber change. Therefore a different scale is necessary for converting this reading. Some vehicles fitted with independent rear suspension incorporates an adjuster for rear wheel alignment.
Fig. 27.21. Trammel wheel track alignment gauge.
Alignment readings are compared to the manufacturer's specifications and appropriate action is taken in case of the difference in readings. The majority of domestic vehicles incorporate a means to adjust both upper control arm pivot points through shims, cams, or slots. Both castor and camber can be adjusted at only one of the pivot points. Some vehicles use an eccentric
adjustment system around the upper ball joint to adjust camber and other use a cam at the lower control arm pivot. In both methods the camber is controlled by changing the relative position of the steering knuckle, spindle, wheel, and tyre. In some vehicle models castor is adjusted increasing or decreasing the length of the lower control arm strut. The front strut-to-frame attachment has adjustment nuts that move the lower end of the knuckle forward or backward to change caster.
Steering axis inclination cannot be adjusted independent of camber, but is used only to check for a bent steering knuckle. When both camber and steering axis inclination deviate from their respective specification range, the knuckle is bent. After the wheel alignment adjustments a road test should always be conducted to ensure that the car tracks straight and is handled properly.
Adjustment of the front wheel parallelism for true rolling also sets the static toe-in or toe-out recommended by the vehicle manufacturer. The adjustment is carried at by increasing or decreasing the length of the track-rod or tie-rods until the correct track-alignment setting is obtained. For correction of the alignment, left and right handed screw threads are provided on the track rod to alter the length of the rod. If the layout has a rack-and-pinion steering box, equal adjustment of the two outer rods is necessary, otherwise the position of the steering wheel alters and the steering locks become unequal.
The trammel gauge, the simplest track-alignment tool, is a horizontal bar that can slide in slots formed in a pair of perpendicular posts that stand on the floor. One post has an adjustable fixed prod and the other post has a spring-loaded prod with a reference scale (Fig. 27.21). To obtain a correct reading, the track alignment should be checked on level ground. The following procedure may be followed for checking the track alignment with the trammel gauge.
(i) The trammel bar is placed across and in front of the steered wheels, with the posts positioned on the outside of each wheel and the prods pointing towards the wheel rims. The fixed prod is set against the wheel inner rim.
(ii) The spring-loaded prod is pulled and released, which presses against the other wheel inner rim and then the scale reading is observed.
(Hi) The points where each prod touches the rim is marked with chalk and then the vehicle
is rolled forward till the wheels turn through exactly 180 degrees, so that the chalk
marks are now at the rear of the wheels. (iv) Now the trammel bar is positioned behind the steered wheels, with the fixed prod just
touching inner rim and the spring-loaded prod free to adjust itself to the inner rim.
The difference in reading between the front and rear measurements gives the toe-in
or toe-out.
Alignment readings are compared to the manufacturer's specifications and appropriate action is taken in case of the difference in readings. The majority of domestic vehicles incorporate a means to adjust both upper control arm pivot points through shims, cams, or slots. Both castor and camber can be adjusted at only one of the pivot points. Some vehicles use an eccentric
adjustment system around the upper ball joint to adjust camber and other use a cam at the lower control arm pivot. In both methods the camber is controlled by changing the relative position of the steering knuckle, spindle, wheel, and tyre. In some vehicle models castor is adjusted increasing or decreasing the length of the lower control arm strut. The front strut-to-frame attachment has adjustment nuts that move the lower end of the knuckle forward or backward to change caster.
Steering axis inclination cannot be adjusted independent of camber, but is used only to check for a bent steering knuckle. When both camber and steering axis inclination deviate from their respective specification range, the knuckle is bent. After the wheel alignment adjustments a road test should always be conducted to ensure that the car tracks straight and is handled properly.
Adjustment of the front wheel parallelism for true rolling also sets the static toe-in or toe-out recommended by the vehicle manufacturer. The adjustment is carried at by increasing or decreasing the length of the track-rod or tie-rods until the correct track-alignment setting is obtained. For correction of the alignment, left and right handed screw threads are provided on the track rod to alter the length of the rod. If the layout has a rack-and-pinion steering box, equal adjustment of the two outer rods is necessary, otherwise the position of the steering wheel alters and the steering locks become unequal.
The trammel gauge, the simplest track-alignment tool, is a horizontal bar that can slide in slots formed in a pair of perpendicular posts that stand on the floor. One post has an adjustable fixed prod and the other post has a spring-loaded prod with a reference scale (Fig. 27.21). To obtain a correct reading, the track alignment should be checked on level ground. The following procedure may be followed for checking the track alignment with the trammel gauge.
(i) The trammel bar is placed across and in front of the steered wheels, with the posts positioned on the outside of each wheel and the prods pointing towards the wheel rims. The fixed prod is set against the wheel inner rim.
(ii) The spring-loaded prod is pulled and released, which presses against the other wheel inner rim and then the scale reading is observed.
(Hi) The points where each prod touches the rim is marked with chalk and then the vehicle
is rolled forward till the wheels turn through exactly 180 degrees, so that the chalk
marks are now at the rear of the wheels. (iv) Now the trammel bar is positioned behind the steered wheels, with the fixed prod just
touching inner rim and the spring-loaded prod free to adjust itself to the inner rim.
The difference in reading between the front and rear measurements gives the toe-in
or toe-out.
hi
ReplyDeleteThe wheel alignment process typically involves measuring and adjusting three main angles: camber, caster, and toe. Camber refers to the angle of the wheels as viewed from the front or rear of the vehicle. Caster refers to the angle of the steering axis, while toe refers to the angle of the wheels as viewed from above or below the vehicle. Winter's Auto Service is a tire and auto repair shop that offers Wheel Alignment Winnipeg services for cars, trucks, and SUVs. They use advanced computerized alignment equipment to ensure accurate and precise alignment. They also offer a warranty on their alignment services.
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