Volkswagen Polo Manual

Wheel alignment and steering angles - general information
Suspension and steering / Wheel alignment and steering angles - general information


Definitions
1 A cars steering and suspension geometry is defined in four basic settings - all angles are expressed in degrees (toe settings are also expressed as a measurement); the steering axis is defined as an imaginary line drawn through the axis of the suspension strut, extended where necessary to contact the ground.

2 Camber is the angle between each roadwheel and a vertical line drawn through its centre and tyre contact patch, when viewed from the front or rear of the car.

Positive camber is when the roadwheels are tilted outwards from the vertical at the top; negative camber is when they are tilted inwards.

3 Camber angle does not normally require adjustment, but refer to Section 6. It can be checked using a camber checking gauge.

4 Castor is the angle between the steering axis and a vertical line drawn through each roadwheels centre and tyre contact patch, when viewed from the side of the car. Positive castor is when the steering axis is tilted so that it contacts the ground ahead of the vertical; negative castor is when it contacts the ground behind the vertical.

5 Castor angle does not normally require adjustment, but refer to Section 7. It can be checked using a castor checking gauge - if the figure obtained is significantly different from that specified, the vehicle must be taken for careful checking by a professional. Where necessary a 3.0 mm washer can be inserted at the anti-roll bar bush on the front of the lower suspension arm.

6 Toe is the difference, viewed from above, between lines drawn through the roadwheel centres and the cars centre-line. Toe-in is when the roadwheels point inwards, towards each other at the front, while toe-out is when they splay outwards from each other at the front.

7 The front wheel toe setting is adjusted by screwing the left-hand track rod (RHD models) or right-hand track rod (LHD models) in or out of its balljoint, to alter the effective length of the track rod assembly.

8 Rear wheel toe setting is not adjustable, and is given for reference only. While it can be checked, if the figure obtained is significantly different from that specified, the vehicle must be taken for careful checking by a professional, as the fault can only be caused by wear or damage to the body or suspension components.

Checking and adjustment
Front wheel toe setting
9 Due to the special measuring equipment necessary to check the wheel alignment, and the skill required to use it properly, the checking and adjustment of these settings is best left to a VW dealer or similar expert. Note that most tyre-fitting shops now possess sophisticated checking equipment.

10 To check the toe setting, a tracking gauge must first be obtained. Two types of gauge are available, and can be obtained from motor accessory shops. The first type measures the distance between the front and rear inside edges of the roadwheels, as previously described, with the vehicle stationary. The second type, known as a scuff plate, measures the actual position of the contact surface of the tyre, in relation to the road surface, with the vehicle in motion. This is achieved by pushing or driving the front tyre over a plate, which then moves slightly according to the scuff of the tyre, and shows this movement on a scale. Both types have their advantages and disadvantages, but either can give satisfactory results if used correctly and carefully.

11 Make sure that the steering is in the straight-ahead position when making measurements.

12 If adjustment is necessary, apply the handbrake then jack up the front of the vehicle and support it securely on axle stands (see Jacking and vehicle support).

13 First clean the track rod threads; if they are corroded, apply penetrating fluid before starting adjustment.

14 Retain the track rod with a suitable spanner and slacken the locknuts. Alter the, length of the track rod by turning the tie-rod as necessary.

15 When the setting is correct, hold the track rod and tighten the locknuts. If after adjustment, the steering wheel spokes are no longer horizontal when the wheels are in the straight-ahead position, remove the steering wheel and reposition it (see Section 13).

16 Check that the toe setting has been correctly adjusted by lowering the vehicle to the ground and re-checking; re-adjust if necessary.

Rear wheel toe setting
17 The procedure for checking the rear toe setting is same as described for the front in paragraph 10. The setting is not adjustable.

Front wheel camber angle 18 Checking and adjusting of the front wheel camber angle should be entrusted to a VW dealer or other suitably equipped specialist.

Note that most tyre-fitting shops now possess sophisticated checking equipment.


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