Tyre Safety
When a tyre is under-inflated, heat builds up inside, which may eventually lead to a drop in pressure. Tyre failure may cause the driver to lose control of the vehicle, which is particularly dangerous on motorways and carriageways.
In the event of a tyre failure, super-single tyres can present the driver with a particular challenge in terms of maintaining control of the vehicle. Other motorists can also be put at risk by any tyre debris left on motorways, carriageways or roads.
Fitting a replacement tyre on a motorway hard shoulder is a highly dangerous activity, especially for larger vehicles. Correct tyre maintenance can greatly reduce these risks and provide a safer working environment for drivers and fitters.
Vehicle Handling & Fuel Economy
The tyre is a complex component of a vehicle that has been engineered to work in harmony with the vehicles sophisticated brake, steering and suspension systems.
When a tyre is under-inflated, the tyre contains insufficient air to support the weight of the vehicle properly, which adversely affects acceleration, braking and cornering.
By keeping tyres at their correct pressure, drivers can travel further on each tank of fuel and help to reduce CO2 emissions. When tyres are under-inflated, the contact patch with the road surface increases, causing increased drag, which in turn places more load on the engine.
The rolling resistance of an under-inflated tyre increases as it requires more energy to return to its original shape after each contact with the road. Keeping tyres correctly inflated helps larger vehicles and commercial fleets to minimise their cost per kilometre rate, while economising on fuel costs.
HGV Tyre Pressure
Keeping tyres inflated to the recommended tyre pressure level for the vehicle ensures even tyre pressure distribution, optimum handling, and consequently a more even wear rate, keeping the tyres in service for longer.
- Driving on under-inflated tyres places excess stress on the tyre shoulders, causing uneven wear towards the outside edge of the tread
- Under-inflated tyres also heat up more quickly than correctly inflated tyres, and in extreme cases can lead to tyre failure
- Over-inflation causes high wear in the centre of the tread
Although HGV tyre pressure should be based on what is recommended by the manufacturer, a general rule of thumb is that pressures should be between 8 and 9 bars (but not above 10). Use this helpful PDF guide from Continental for more specific measurement recommendations.
Legal HGV Tread Depth for Tyres
Current tread depth legislation requires that HGV tyres must have a minimum of 1mm of tread in a continuous band throughout the central three-quarters of the tread width and over the whole circumference of the tyre. The same regulation applies to regrooved tyres.
You may be thinking “but why is it 1.6mm for cars?” and there is good reason for this. HGVs are significantly heavier than cars and tread depth relates to grip on the road. It’s much easier for a HGV to dispel water and maintain grip than your average car.
When driving in wet weather, the tread pattern of the tyre helps to evacuate surface water from the road. As the tread begins to wear down, the tyre gradually loses the ability to evacuate all the water from the road surface, which increases stopping distances in the wet. The lower the tread depth, the greater the risk of aquaplaning.
Wheel Alignment & Regrooving
Incorrect wheel alignment, especially when caused by damage from potholes, may cause the tyres to scrub against the road surface to a greater degree, increasing wear and rolling resistance.
For example, if any of the wheels of a 12-wheel tractor and trailer are not properly aligned, the total drag on the vehicle increases.
Misalignment may also cause greater aerodynamic drag when the tractor and trailer are not tracking parallel to the direction of travel.
Any tyre regrooving should take place at around 4mm of remaining tread. After regrooving, the 1mm law still applies. It is also written in law that the tyre is regrooved in the pattern designated by the tyre manufacturer. Failure to observe this will render the tyre illegal.
If any of the tyre’s cords are exposed during regrooving, the tyre should be disposed of immediately. [N.B. It is important to consider that budget tyres might not be designed with enough extra rubber to regroove tyres.]
Correct Torque for HGVs
HGV tyres have been known to come loose and cause untold damage and risk to life. The wheel nuts need to be tightened to a specific torque setting, as dictated by the manufacturer. Improper torque (too loose or too tight) can lead to wheel detachment, which is a major safety hazard.
Most HGV’s have fluorescent plastic indicators on the wheel nuts. These are visual aids that are fixed to the wheel nuts in a recognisable pattern – such as point-to-point – meaning any movement on the wheel nuts themselves can be easily noticed by the truck driver or fleet operative during a routine inspection. They also deform when the tyre wheel gets too hot, which may indicate other underlying issues such as worn brakes.
These indicators are a helpful secondary check, but not a substitute for using a torque wrench. Over time, they can become damaged or unreliable. You need to use a properly calibrated torque wrench to tighten wheel nuts.
HGV Tyre Maintenance Tips
- Regular visual inspections for damage, cuts, bulges or abnormal wear.
- Ensuring correct tyre pressure inflation (improves fuel efficiency, handling and reduces wear).
- Wheel alignment checks to prevent uneven wear.
- Visually check for misaligned or melted wheel nut indicators and re-torque, if necessary.
For more information, please see the British Tyre Manufacturers’ Associations guide to tyre management and maintenance on heavy vehicles.
Safe Tyre Disposal
Tyre disposal companies can be hired to remove end-of-life tyres and transport them away for shredding.
The Responsible Recycler Scheme offers one such service to fleet companies. It operates under license by the Tyre Recovery Association and collector members of the scheme can be located by postcode on the website.
After reprocessing, tyre derived products can then be used for various purposes, such as landfill drainage, coastal defense, road surfacing products and children’s playgrounds.