The importance of correct wheel alignment

Issue: Summer 2009

A Freight Best Practice Case Study

WHEEL ALIGNMENT/BEST PRACTICE

If the wheels on trucks are misaligned, even by only a small degree, it can have an adverse effect on both tyre wear and fuel consumption, as the engine has to work harder to make the vehicle move. To highlight the matter, the problems it can cause, and the potential savings that can be gained with the issue being addressed, Freight Best Practice has a publication, Keeping Profit on Track with Wheel Alignment, which examines the question in detail.

Visible signs of wheel misalignment include wear on the tyre shoulder or an uneven wear over the tyre tread. Wheels can be out of alignment for a number of reasons, for example, a steering joint may have been replaced, the vehicle may have nudged a kerb, or the vehicle might regularly run off-road, over uneven ground. To reduce tyre wear and avoid unnecessary fuel use, wheels should be realigned to within specific tolerances.

For many operators, wheel alignment has been an integral part of a preventive maintenance programme for some time. Basic alignment methods use a mechanical gauge with manual calibration being carried out by eye. However, as fuel and tyre costs have increased, some operators have turned to laser technology as a more accurate method of wheel alignment.

What are the aims of wheel alignment?

For steered axles:

• To achieve correct ‘toe in’/’toe out’ (the degree to which wheels are turned towards the centre or towards the outside of the vehicle).

For drive and trailer axles to make them:

• Square to centre line of the chassis.
• Parallel across the axle.  Parallel between axles.

Using laser equipment, the procedure aims to align to within 0.15° accuracy.

What are the potential benefits of ensuring wheels are correctly aligned?

The potential benefits of carrying out wheel alignment are:

• Reduced fuel usage (a 1° misalignment on one axle could increase fuel consumption by around 5%)
• Improved tyre life (a 0.5° misalignment can reduce tyre life by up to 50%). 
• Reduced carbon dioxide and other harmful emissions. 
• Less stress on mechanical components. 
• Improved driver comfort and safety.  
• Reduced potential for tyre overheating.

The process of laser wheel alignment

The process of laser wheel alignment involves fitting the vehicle at the front and rear with bars with measuring gauges attached. Devices are then fitted to each wheel, complete with laser lights. These laser lights on each wheel are lined up with the gauges on the front and rear bars, to measure the amount of ‘toe in’ and ‘toe out’ of each wheel. Having taken these measurements, simple adjustments can be made and wheel realignment achieved. The diagram below illustrates the procedure.

How often should wheel alignment be carried out?

Wheel alignment can offer most benefit if repeated at least every 12 months. Companies are advised to incorporate wheel alignment in their annual pre-MoT inspection.

Between planned annual wheel alignment procedures, regular vehicle safety inspections include monitoring of tyre wear. If noticeable uneven wear is detected at any time during the year, realignment is carried out.

It may also be beneficial to carry out the process before a new vehicle is put into service, to ensure all wheels are accurately aligned. If a vehicle has been involved in an accident and repaired, calibration should be rechecked before the vehicle is put back into service.

The tyre in the photograph has completed 220,000 kms and shows some uneven wear due to misalignment. However, if action is taken to rectify the problem then the expected life could be extended to over 300,000 km

How much might laser wheel alignment cost?

Calibration costs vary depending on the type and number of vehicles in the fleet. However, the table below gives some guidance of approximate costs:

Fleet fuel and tyre savings

Significant savings and potential benefits might well be achieved through a wheel alignment  programme. The costs of wheel alignment and fuel are indicative and relate to the fact that larger  fleets may be eligible for discounts. 

Conclusion

It makes sound operational and financial sense to make sure that the wheels on your vehicles are correctly aligned.  A programme of laser wheel alignment implemented as part of a preventive maintenance programme, can lead to increases in tyre life and improved fuel efficiency. Correct wheel alignment can also lead to less wear and tear on vehicle components and reduced driver fatigue, as vehicles become easier to drive. 

Note: Freight Best Practice was assisted in the compilation of Keeping Profit on Track with Wheel Alignment by Steertrak, Kidds Transport and CRL Distribution

Keeping Profit on Track with Wheel Alignment and other Freight Best Practice publications can be obtained free of charge by calling:  0845 877 0877. Alternatively they can be downloaded from the website:  www.freightbestpractice.org.uk 

Published: 06/07/2009