They are just round black things which cost a lot of money, but our understanding of tyres and how to utilise them seems to attract a lot of old wives’ tales, so tyre pressure, is it all just hot air?
Diesel Workshop tries to get to the heart of tyre pressure issues.Looking at problems around tyre pressure and working though the alternatives when it comes to managing the issue in a trucking fleet has a number of potential issues.
There are some basic things we need to understand about a tyre before we go into the technical realities of running tyres in a modern trucking fleet. The tyre is the only connection between the truck and the ground, and the medium which is holding the truck off the ground is, in fact, the air within it. Tyres are a very important component in any trucking operation, coming third behind wages and fuel in terms of costs.
Not only does the tyre hold the truck up from the ground, it is also an important safety feature, keeping the truck in a straight line and enabling it to go around corners safely. It is also vital that it has the correct friction coefficient to stop the truck in an emergency. The air in the tyre also has the effect of reducing vibration and noise from the road entering the truck and improving ride both for the driver and for the freight.
Tyre pressure is a very important factor in the performance any tyre. With the kinds of masses truck and trailer tyres are carrying it becomes an even more important factor, pressures become more critical. Tyre pressure has a direct effect on the tyre’s overall performance, fuel economy and the life of the tyre. When looking at truck tyres, studies have shown that more than 80 per cent of tyre problems are caused by under inflation.
The problem is there are no fixed rules on what is the right tyre pressure for each individual tyre in any particular situation, it depends upon the load the truck is carrying, the speed the truck is travelling at and the conditions of the road itself.
Tyre manufacturers do provide load and pressure tables, but operators will tend to err on the side of caution and run at higher pressures than would be ideal. Also, if tyres are running at too high pressure and not getting checked, they are less likely to be running at less than ideal pressures.
Running a tyre at a higher than ideal pressure does cause some problems and can lead to uneven wear in the tyre. Over-pressure tyres get three times the punctures, stone bruises, cuts and uneven wear. They cause damage to suspension, drive line, roads trailers and trucks, thus increasing maintenance costs and break downs.
However, running at too low an inflation pressure can cause bigger problems. Tyres running on low pressure will tend to heat up quickly and the tyre will reach a temperature at which the rubber starts to degrade quickly. Tyre wear in this case can be quite catastrophic.
A rule of thumb is that if a tyre is running at 20 per cent below the correct pressure for that load, it’s life span will be decreased by more than 20 per cent. A trucking operator only needs to have a look at the monthly tyre bill once to see just how much 20 per cent tyre life actually costs.
Here we have the basic problem, maintaining the correct tyre pressure at all times costs in both time and money. Running tyres with a pressure which is too low can also be extremely expensive. Running with a pressure which is a little bit too high is not so expensive and can reduce the possibility of the truck running with low tyre pressures, but will also reduce tyrelife and compromise braking ability.