94 Steering geometry and wheel alignment

9.4.1 Wheel track alignment using Dunlop optical measurement equipment — calibration of alignment gauges

1 Fit contact prods onto vertical arms at approximately centre hub height.

2 Place each gauge against the wheel and adjust prods to contact the wheel rim on either side of the centre hub.

3 Place both mirror and view box gauges on a level floor (Fig. 9.25(b)) opposite each other so that corresponding contact prods align and touch each other. If necessary adjust the horizontal distance between prods so that opposing prods are in alignment.

4 Adjust both the mirror and target plate on the viewbox to the vertical position until the reflection of the target plate in the mirror is visible through the periscope tube.

5 Look into the periscope and swing the indicator pointer until the view box hairline is positioned in the centre of the triangle between the two thick vertical lines on the target plate.

6 If the toe-in or -out scale hairline does not align with the zero reading on the scale, slacken off the two holding down screws and adjust indicator pointer until the hairline has been centred. Finally retighten screws.

1 Ensure that tyre pressures are correct and that wheel bearings and track rod ends are in good condition.

2 Drive or push the vehicle in the forward direction on a level surface and stop. Only take readings with the vehicle rolled forward and never backwards as the latter will give a false toe angle reading.

3 With a piece of chalk mark one tyre at ground level.

4 Place the mirror gauge against the left hand wheel and the view box gauge against the right hand wheel (Fig. 9.25(b)).

5 Push each gauge firmly against the wheels so that the prods contact the wheel on the smooth surface of the rim behind the flanged turnover since the edge of the latter may be slightly distorted due to the wheel scraping the kerb when the vehicle has been parked. Sometimes gauges may be held against the wheel rim with the aid of rubber bands which are hooked over the tyres.

6 Observe through the periscope tube the target image. Swing the indicator pointer to and fro over the scale until the hairline in the view box coincides with the centre triangle located between the thick vertical lines on the target plate which is reflected in the mirror.

7 Read off the toe-in or -out angle scale in degrees and minutes where the hairline aligns with the scale.

8 Check the toe-in or -out in two more positions by pushing the vehicle forward in stages of a third of a wheel revolution observed by the chalk mark on the wheel. Repeat steps 4 to 7 in each case and record the average of the three toe angle readings.

9 Set the pointer on the dial calculator to the wheel rim diameter and read off the toe-in

in rgH^out


Fig. 9.25(a-c) Wheel track alignment using the Dunlop equipment calculator

Fig. 9.25(a-c) Wheel track alignment using the Dunlop equipment or -out in millimetres opposite the toe angle reading obtained on the toe-in or -out scale. Alternatively, use Table 9.1 to convert the toe-in or -out angle to millimetres.

10 If the track alignment is outside the manufacturer's recommendation, slacken the track rod locking bolts or nuts and screw the track rods in or out until the correct wheel alignment is achieved. Recheck the track toe angle when the track rod locking devices have been tightened.

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