Tyre design is changing to meet the ever increasing demand for better fuel economy. There are two key areas that tyre manufacturers are working with.
The first is reducing the weight of the tyre.
This has been achieved be making the tyre wall thinner and decreasing the depth of the tyre tread. The second is by tyre companies developing low rolling resistance constructions and tread compounds.
Laboratory tests in the United States have highlighted the importance of these attributes in modern tyre design. With a vehicle in stop/ start driving conditions the results of these studies suggest that the rolling resistance of the tyres account for 15% of the vehicles overall resistance. The other resistance factors are overcoming inertia 35%, driveline friction 45% and air resistance 5%.
With a vehicle driving at highway speeds the air resistance (or drag) increases to approximately 60%. The rolling resistance of the tyres if set at correct pressure climbs to 25%. If the tyre pressure were to drop by seven psi the rolling resistance increases by approximately one eighth.
To be precise a tyre is not actually round.
That’s right, this is for two reasons, the manufacturing process and the way the tyre behaves on the road.
A tyre can form what is known as a stiff spot.
This is created by the joins in the steel wire layers, the fabric and the rubber. This can produce a vibration when the tyre is used on the road. Tyre manufacturers combat this by precisely measuring the tyre for the stiff spot or (non-uniformity) and removing a small amount of tread rubber from the stiff spot area.
When a tyre is fitted onto a vehicle and carrying a load it is no longer round. As the tyre rolls, it distorts to form a flat contact patch on the road surface. Subtle bulges form just in front and at the rear of this contact patch. The greater the tyre distortion at the point of road contact the greater the friction and resulting heat build up in the tyre. This heat build up is the enemy of tyre life.
The tyre manufacturers aim is to design a tyre with a maximum contact patch (for grip) and reduce distortion to minimise the heat build up in the tyre. If you let your tyre pressures drop then you undo all that design work and greatly reduce the life of your tyres.
Did you know that tyres are not naturally black?
The tyre manufacturer makes them black by adding a compound called carbon black. This is an important additive for production and appearance. The natural colour of the rubber is grey and the carbon black is a filler used to extend the rubber. It forms part of the complex chemical mixture that gives the tyre adhesion. Tyres could actually be any colour the manufacturer wanted them to be.
Nitrogen filled tyres – is it worth it?
The compressed air that is used in tyres naturally has 78% nitrogen and 21% oxygen. However there are benefits to using pure nitrogen in your tyres. Tyres filled with nitrogen will remain at a constent pressure regardless of the change in the temperature of the tyre itself.
The use of pure nitrogen will result in maintaining the correct tyre pressure for longer. The oxygen in compressed air will slowly leak through the rubber walls of the tyre approximately three times faster than if the tyre was filled with pure nitrogen.
Lower tyre pressures will result in higher costs to you.
A vehicle with low tyre pressures will react slower to the driver’s steering input and have an increase in braking distance. The tyre itself will wear out much quicker and there will be an increase in fuel consumption due to the increase in drag on the road surface.
Silica based tyres – revolutionising tyre technology.
The introduction of silica into tyre manufacture has been a huge step forward for the tyre industry. Silica is used to replace some of the carbon black in the tyre’s tread compound. The result is that the silica has helped to overcome some traditional technology and design problems.
Before the introduction of silica, tyres had either good wet weather grip and a higher rolling resistance (not good for fuel economy) or low rolling resistance (better fuel economy) but less traction in wet weather not both. Now with the option of silica based tyres for your vehicle you can have the best of both worlds.