For many people tyres are just those black things on a vehicle that they have to check when they look a flat. Dirty fingers, all that bending over – it’s definitely not a pleasant task. The only other time you hear about them is when the car is getting serviced and the mechanic informs you that you need new tyres.
Ugh – suddenly this trip to the mechanic is costing you even more! Sadly, this is how many road users view their tyres. Given how vital they are for your safety on the road, there’s actually a lot more to know about tires, and we feel that it’s something that most people could do with a bit more education on.
Tyres 101: How They Work & What You Need To Know
When a tyre is rolling down the road it consumes energy. On a vehicle this energy is provided by the fuel. The degree of resistance to rolling is caused by many factors:
the design of the tread pattern,
the casing of structural members of the tyre,
the road surface itself,
and the largest factor of them all is the inflation pressure of the tyre.
Remember getting your push bike home when it had a flat tyre? It was a lot of work wasn’t it? The road surface hadn’t changed, only the inflation pressure of the tyre.
Hysteresis & Vehicle Speed
When a tyre supports a load on a vehicle it deforms under load. There is a technical term known as hysteresis, this explains the way a block of rubber is deformed and the energy it consumes. The higher the load, the higher the deformation, it’s that simple.
With an increase in vehicle speed comes an increase in the frequency of the deformation - but there’s a catch. The faster the vehicle travels the greater the deformation caused by the load. A small bump in the road at slow speed can be a large bump at high speed. So, the energy consumption due to hysteresis is exponential. A technical way of saying the faster we go the more energy we consume.
A tyre moving about the suburbs travelling slowly, not carrying a lot of load barely increases in pressure. The same vehicle travelling at highway speed shows, with properly inflated tyres, we observe an increase of up to 15% over the cold setting. Put some load into the vehicle and suddenly the tyres are over working, the operating pressures are heading north of 15% indicating the tyre is overworking.
A tyre supports the load imposed on it with the air contained inside. The higher the load the more air required. Remember the hysteresis? The faster the vehicle travels equals the more air the tyre requires. So, when you’re driving around the city with a light load your tyres aren’t working. As soon as you add more load and start going faster your tyres require more air to support the load and speed.
Heat & Tyre Damage
When a tyre is formed it is a one-way process that combines chemicals and raw rubber to form what we know as a tyre. It’s not like freezing water where when it defrosts it turns to water again. Making a tyre is like baking a cake, when it’s made that’s it. It can’t be unmade.
When a tyre reacts to work on the road it generates heat. It generates a lot more heat than just sitting in the sun, and you can’t tell how hot a tyre really is just by feeling it. The heat is inside the tyre structure. By the time you can smell it and think “wow that tyre is hot” the damage is done - the cake is burnt. By this time the inflation pressure will have increased probably well beyond 25% above the cold pressure, which is far too much.
Tyre manufacturers suggest that for road use pressures should be in the 10% ‐ 15% range. Any higher than that the tyre is overworking. In specialist tyres like motorsport and the giant haul truck tyres the pressures do go higher, but those types are working a lot harder than normal road tyres and are designed to handle the strain.
I prefer to set mine at 19% above cold, yes there are times when I work the tyres hard, I carry a big load and I know this is worth 2 – 3 psi on the run home. If you have monitoring technology installed and get an alert that the tyres are in danger of overheating, the easiest way to cool the tyres is to slow down. Remember that exponential increase? It works the same in reverse too, just 10 km/hr will make a lot of difference to the work a tyre does at highway speed.
Understanding The Effects Of Tyre Pressure
Under pressure is where damage is done quickly. If I ask you to carry a heavy load you can walk well enough, but if I ask you to start running then you will perish quickly, a tyre is no different. So why is this important?
By not understanding how tyres are performing users burn up a lot more fuel (remember pushing the bike home?) and wearing tyres out a lot faster. There’s a double loss which compounds over time. The result is tyres are changed more often, you can’t sell the casing or use them for retreading either, but worst of all is endangering cargo and other road users.
If a tyre is underinflated and it fails catastrophically, (yes like the road gators you see on the roadside) then there is a potential loss of control. Tyres may be just those dirty black things on a vehicle for most road users, but they make the world of difference in operating efficiently and safely. Plus think about how you can also reduce your environmental impacts with some simple tyre habits.
What are your tyre habits and how does your organisation approach managing their tyre risk?
Good Tyre Safety Habits
A few good habits to get into are:
Check your tyres weekly.
Consider your load and pressure as part of a journey plan.
Check you have a working spare before long trips.
Consider whether a tyre pressure monitoring systems will make life easy.
Purchase reputable brands, they cost more up front but save in the long term.
If you’d like to learn more about the importance of good tyre safety and purchase products that can help keep you moving towards your destination, get in touch with us today.