Car Tyre Guide

Do you want to maximise your fuel economy, help the environment by reducing your CO₂ emissions and save money by reducing tyre wear. To achieve the goals above, and for your car to be safe on the road, ongoing monitoring of your tyres and their pressures is vital.

Tyre maintenance is extremely important especially at this time of the year when the roads can be treacherous due to snow and rain. Have you checked your tyres lately? It could mean the difference between life and death on the roads this Christmas.

The importance of correct tyre pressure

The correct tyre pressures on your car will improve your fuel economy, reduce your CO₂ emissions and save you from buying new tyres unnecessarily.

You must also regularly monitor the pressure of your tyres if you want your car to be safe on the road.

Over inflating or under inflating your tyres can make the handling of your vehicle unpredictable.

Identifying correct vehicle tyre pressures

The first place to go to check that your tyre pressures are correct is your car’s handbook. Information is also often provided on a label just inside the drivers door side of the car in the bottom corner. The spare tyre will have its pressure written across the side if it’s the narrow, slim line type.

We should all check our tyre pressures periodically, especially before long journeys, and remembering to include the spare. Also keep in mind that there is a slight difference (for some vehicles) in pressure recommendations for half loads and full loads in the car. Consult your handbook or label at the pillar of the drivers door for more information.

If your tyre are under inflated you will use more fuel, you will also cause excessive wear to the edges of the tyres, which will shorten their life.

Putting too much air in your tyres can cause unpredictable handling and accelerate tread wear across the centre of the tyre.

A good tread on all tyres is especially important for grip in wet conditions.

Your tyre grip is crucial

How well a tyre grips the road surface depends primarily on its rubber compound and the grooves that form the tread pattern. Remember, it's the tyre surface that's in direct contact with the road that does all the hard work.

In wet conditions, water lessens the contact between the tyre and the road, reducing grip. Taken to extremes, the result is aquaplaning. This occurs when there is no direct contact between rubber and road, resulting in a loss of control.

The tread grooves are designed to expel water from between the tyre and the road. Each manufacturer designs its own tread pattern to achieve this.

The more efficiently the grooves expel the water, the better the tyre will be at maintaining grip in wet conditions.

In dry conditions, the friction between tyre and road is the main factor in maintaining grip. If you brake harshly, accelerate rapidly or take a corner too fast, the tyre may slip and tyre wear will be accelerated.

However, tread on the outside edges should be "visible"

Tread depth of the tyre

The legal minimum tread depth for cars (including caravans) up to 3500kgs gross vehicle weight and for 8 seated passenger vehicles including driver is a minimum of 1.6mm in a continuous band throughout the central three-quarters of the tread width, maintained throughout the whole of the tyre circumference.


Driving with a heavy load in your vehicle

If you're carrying heavy loads, you'll need to increase the air pressure in your tyres to compensate. This is very important to maintain safe handling, remember that the load not only includes the baggage in the boot but also the amount of passengers in your vehicle. Another important point is some car headlights need to be adjusted to suit the heavy load in the car.

You can find the correct tyre pressures for heavy loads in your car’s handbook.

Always remember to readjust your tyre pressures when you return to using your car as normal. (and don’t forget the headlight adjustment)

How to read your tyres.

Understanding the markings on the sidewalls of your tyres will help you choose the right replacements for your car.

The letters and numbers on the side of your tyres relate to their size, dimensions, composition and capabilities.

Here’s what each section of the code means, using the tyre size and specification 175/65 R14 T as an example:

• 175 - tyre width in mm

• 65 - tyre sidewall profile – sidewall height expressed as a percentage of its width

• R - radial (rather than a cross ply)

• 14 - diameter of the wheel rim, in inches

• T - speed rating which must match, or exceed the maximum speed of your car.

Tyre speed ratings

• S 180 km/h or 112 mph
• T 190 km/h or 118 mph
• U 200 km/h or 125 mph
• H 210 km/h or 130 mph
• V 240 km/h or 149 mph
• W(ZR) 270 km/h or 168 mph
• Y(ZR) 300 km/h or 186 mph
• ZR Above 240 km/h or 149 mph

Your car’s handbook will tell you the minimum tyre speed and load ratings you should go for. Never go lower than this.

Elsewhere on your tyres you will see the manufacturer’s name, the tyre type and information about where and when the tyre was made.

Run flat tyres

Run flat tyres are an increasingly popular type of tyre that allow you to keep going after a puncture. If you are unlucky enough have a puncture on your journey or if the tyre deflates, a run flat tyre supports the vehicle weight, so you can travel on for about another 50 miles, at a lower maximum speed usually up to 50mph. (Please check your handbook for speed confirmation)

There are many markings that could indicate your tyre is a ‘run flat’ tyre, including DSST, RFT, ROF and RunFL. Run flat tyres and traditional car tyres should not be mixed on the same car, as it could affect vehicle handling. Some tyre companies advise that run flat tyres should not be used without a pressure monitoring system, this automatically alerts the driver of a deflation or puncture.

TOP TIPS FOR INCREASING FUEL ECONOMY

• Change up early through the gears. Shift up between 1.700 and 2.500 revolutions (depending on vehicle).
• Ensure you adopt a smooth style of driving – ease into acceleration.
• Avoid tailgating. Keep your distance between vehicles to ensure you brake smoothly.
• Reduce your speed, driving at 110 KPH uses 15% more fuel than at 80 KPH.
• Use Cruise Control for Motorway driving to maintain a constant speed, as this can give 7% average fuel savings.
• If you are stopped for more than 40 seconds (e.g. at a level crossing), save fuel by switching off the engine.
• Use the Air Conditioning sparingly as it can reduce fuel consumption by as much as 20%.
• Check tyre pressures regularly.
• Ensure your vehicle is serviced regularly.
• Remove unnecessary weight from the car (golf clubs, roof racks etc), when not required.