Everybody knows earthmoving tyres are as rare as hens' teeth at the moment.But are you aware of the steps that can be taken to prolong tyre life? Paul Howard speaks to Bridgestone to find out more
HOW DO you look after a tyre? How do you ensure it wears as slowly as possible and doesn't fail? If you think the only people interested in the answers to these questions are white-coated research scientists at tyre manufacturers, you obviously don't run a fleet of mobile cranes or heavy earthmoving machinery. If you do, you'll realise just how important looking after tyres has become in these days of global tyre shortages, likely to last for another two years at least.
Barry Coleman, product manager for earthmoving tyres at Bridgestone, says that by anyone's standards the situation is extremely tight.
'Tyres are going straight from the dock to our customers.We would normally carry between 250 and 300 2700R49s for 100-tonne rigids - this stock has gone.The global demand for commodities, which has fuelled the demand for plant and tyres, is even affecting shipping. Costs have gone through the roof.We've got tyres sitting on the quayside in Japan because we couldn't get a container. Even when tyres do arrive in the UK we're allocating them, not selling them.We simply can't supply all the people who want them.'
Thus, he says, practicality demands a more cautious approach to the tyres you've got.'It has got to the point that operators should maximise the life of their tyres even at the expense of operating their quarries and mines slightly less efficiently.'
Mr Coleman has a surprisingly long list of measures that can be taken to get the most out of your tyres and he is unapologetic if some of them seem obvious.
'I don't want to preach but the pinch point is the supply of tyres so it's important we provide the information to people so they can choose what to do. It's not rocket science, just good 'tyre husbandry'.'
The first, and most obvious, step is to ensure tyres are used at the correct pressure (before you start ranting against such apparently patronising advice, consider how often you check the tyre pressure in your car).
'You must make sure the pressure is checked regularly. It's amazing how often it isn't as it should be, ' says Mr Coleman.'The tyre pressure in a rigid truck is nominally 100 psi; if it's running at 90 psi this would probably reduce tyre life by 13 per cent.
'Normally this cost would be difficult to identify or quantify as part of a broader picture of doing the work that needs to be done but now it ought not to be thought of as simply extending tyre life - it should be thought of as allowing you to prolong production by 13 per cent, being able to take advantage of the bull market for commodities for 13 per cent longer.'
And what does 'regular'mean? Daily checks.
'Under normal circumstances you might want to check pressures weekly but a weekly inspection may not pick up on a leak until it's already caused the tyre to wear prematurely or even fail. If you check them daily you'd see this, ' he says.
While checking the pressure, don't forget to check for signs of cuts and damage as well. In this case, a stitch in time really does save nine.
The second bit of advice is to avoid overloading and high speeds.Given that the air in the tyre is there to carry the load and the correct tyre pressure is determined by the load to be carried, it follows that overloading a truck is the equivalent of under-inflating the tyres.The simple conclusion is that by avoiding overloading you can extend tyre life.
'We weigh vehicles when we check the pressures and it's uncommon not to find them overloaded. Basically, the trucks are run as heavy as you can safely get away with. It doesn't normally cause any problems but it is bad for tyre life, ' says Mr Coleman.
High speeds can cause similar problems: the faster you drive, the more heat you put into a tyre, the more it will wear.'In hotter climes, driving too quickly generates more heat which causes tyres to wear more, ' he says.
You may also want to reconsider the merits of repairing rather than scrapping worn tyres.'Last year, it might not have been cost-effective, but it may be now, 'Mr Coleman points out.'If a tyre was 80 per cent worn you might have thrown it away; now it may be cost-effective - in terms of being able to produce for longer - to repair it for that remaining 20 per cent.'
Another vital step is to ensure that you use the correct specification of tyre for the task in hand.This may seem like stating the obvious but the shortage of tyres is so acute that some operators have been tempted to use lower-quality and sometimes illegal tyres imported from abroad in lieu of premium brands.
'Instead of premium radial tyres on rigid trucks, they are now using cross-ply tyres from Russia or China. It's not ideal, but if it keeps a machine running, ' he says.
Another option used by increasingly desperate end users has been to take tyres designed for different markets, such as Africa. But this strategy presents its own set of risks.
Mr Coleman explains: 'These may look exactly the same, but they'll have a different tread compound and a different construction. If they're from Africa they'll be designed first and foremost to deal with heat, whereas in the UK the biggest issue is to cut resistance.'
This difference in design can reduce tyre life by up to 60 per cent and in extreme cases can lead to tyre failure.'There was a death in South America last year due to fitting the wrong type of tyre, ' he warns.
The shortage is not restricted to large earthmoving and mining machinery - the same situation applies to mobile cranes and has lead to some owners using illegal imports.'We know of mobile crane operators importing tyres from the USA.These are premium brands but they're not Emarked - the tyre equivalent of CE marking.'
Whatever specification of tyre you use, you must be prepared to act quickly if you see irregular wear patterns developing.This is particularly the case when tyres are twinned, as at the rear of rigid trucks, says Mr Coleman.
'It's very important both tyres have the same tread depth. If not, one carries more of the load than the other, which actually means that the smaller tyre - the one with less tread - wears more quickly, although the wear life of both is seriously compromised.'
You should also insist on the correct mounting of tyres on to clean and well-maintained rims.
The inspection of simple components - 'O' rings and valves - is another key task.
'It's important not to penny-pinch.These are relatively cheap but if they go they can lead to tyre failure. It's easy to talk about under-inflation and its impact on tyre life but most leaks are down to not having a high-pressure valve cap.'
Systems such as Bridgestone's Tyre Monitoring System may also help.'We inspect rigid truck tyres every six weeks and we can work out the wear rate for each tyre and its anticipated life, ' says Mr Coleman.
This information allows operators to budget accordingly and pre-buy where necessary. It may also allow the diagnosis of uneven wear on certain machines, and highlight opportunities to improve maintenance or training at machine-specific levels.
Apart from the tyres themselves there is an array of other ways to prolong tyre life. Site maintenance, both of the haul roads and at the quarry face, is crucial, as is minimising road gradients.Above all it's vital to make sure this information is disseminated to all levels on site.
'You must keep operators - not just quarry managers - aware of just how important an asset tyres are at the moment, 'Mr Coleman insists.
'When it comes to operation and maintenance, most operators are good and professional and so are dealers, inspired as much as anything else by increasing health and safety awareness.Now you need to make sure they're 100 per cent on this.'