Understanding wheel alignment geometries can lead to increased work

To the untrained, Wheel Alignment can appear to be a mystifying artform. However, once the basics principles are grasped, Wheel Alignment services can be added to any workshop. With some workshops still only offering tracking, a 4-wheel alignment solution offers a more accurate solution for the customer. Unless the rear axle thrust of the vehicle is taken into account, a vehicle that has just had it’s tracking measured and adjusted can crab down the road instead of all wheels pointing in a straight line. If you are only relying on front tracking gauges, the kit to 4 wheel alignment perfection does not need to be prohibitively expensive.

 

Here at Supertracker, we stress the importance of going back to basics to understand what wheel alignment angles mean, common forms of misalignment and how to conduct a wheel alignment check in the correct order. This is particularly important to thousands of garages already using Supertracker laser alignment systems.

 

The common forms of wheel misalignment

 

Referencing the rears before adjusting the fronts in wheel alignment checks is a crucial first step for ensuring accurate and comprehensive alignment adjustments. By prioritising rear wheel alignment, technicians ensure a stable baseline, address potential suspension issues, optimise vehicle stability and handling, and enhance the efficiency and accuracy of the alignment process. This systematic approach helps deliver superior alignment results that contribute to improved vehicle performance, safety, and overall driving experience.

 

Geometry misalignment can manifest itself in several ways. Five of the most common issues are issues with front toe, rear toe, thrust angle, camber, and castor.

 

Front toe

Front toe issues refer to the wheels pointing outwards from the vehicle central line if viewed from above. Should the wheels be pointing inward, towards the centre line, this is referred to as toe in, or positive toe. Should the wheels at the front or rear of the vehicle be pointing outwards, this is known as toe out, or negative toe.

 

Rear toe

Rear toe assists the straight-line ability of a vehicle, as it is based around an axle that experiences no directional movement. Should the wheels not be set equally on both sides, a thrust angle is introduced. Both front and rear toe are crucial to reduce wear on wheel and suspension components, where tensions can be built up without the correct geometry angles.

Vehicles with toe in or toe out problems will experience increased tyre wear across the whole of the tread. This is due to the wheels experiencing a slight sideways force as it travels forwards, effectively ‘scrubbing’ the tyres across the road surface. If drivers are reporting that tyre life is shorter than expected, the toe angles are a good place to start any investigation.

 

Thrust angle

The trust angle is the angle of the central line of a vehicle in relation to the rear axle. This should equate to 90-degrees from the rear axle which, in turn, means there is a zero-degree thrust angle.

 

 If the thrust angle is greater than zero, this will start to affect the relationship between the front and rear axles. With the rear axle helping to keep a vehicle travelling straight, this deviation would require compensation with the driver experiencing their steering wheel pull to the left or the right, a situation that leads to ‘crabbing’. To counter this, technicians need to amend the front toe values, commonly referred to as the ‘thrust angle compensation’.

 

Another common issue experienced by drivers is inconsistent tyre wear on the inside or outside shoulder of the wheel. This can be an indication of issues around camber. Wheels should sit vertically, without any lean inwards or outwards. Any deviation leads to more pressure on the edge of the tyre, as it presses into the road, while the opposite side experiences less force against the surface.

 

 Camber

Camber is set to help vehicles when cornering, keeping the centre of the tyre in contact with the road. These angles must be equal on each side of the vehicle, or the driver will experience drifting to the left or right without steering correction.

Negative camber sees the top of a wheel leaning into a vehicle, and affects the inside shoulder of the tyre. Positive camber means a wheel is leaning away from the vehicle, affecting the outside tread. Spotting these trends can offer an insight into misaligned geometry.

 

Finally, for wheel alignment geometry to remain as consistent as possible when a vehicle is moving, a castor angle is built in. This is the angle at which suspension components sit, leaning back from the vertical line of a wheel to push when in motion and reduce tension on components.

 

Castor angle

Castor angle is only adjustable in a few vehicles, and problems are likely the result of accident damage. Both castor angles on vehicle wheels do not need to match, as UK vehicles are often set with the left castor slightly higher than the right, to compensate for road camber.

 

 

 Supertracker 4 Wheel Alignment Systems

We are dedicated to offering customers wheel alignment systems and support to suit their individual needs. With a simple, yet accurate range of laser and computerised wheel alignment systems, backed by a nationwide aftercare support team, we can help advise on the right equipment for you, with training and demonstrations available in our new dedicated training studio.

 

If you’d like to know more about wheel alignment please speak to our experts on 01909 480055, email info@supertracker.com or visit Supertracker’s wheel alignment training studio.