HINTS FOR HAULIERS.
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Tyres—Their Life, the Cost of Maintaining Them and of Their Renewal. The Cost Expressed as a Weekly Oaf ay.
HAVE, in three previous articles., dealt with the collection and preliminary recording of accounts in _connection with expenditure on fuel, lubricants and sundries, or maintenance. In the last article I warned readers against the danger of not making proper provision against the time when tyres would have to be renewed, my experience being that the average man, careful of his tyres when they are new, and watchful of their condition, is so reassured by their apparent longevity that he soon forgets about them altogether, until the urgent need for their renewal is forcibly brought to his notice, when, often enough, he finds it difficult to afford the money to buy new ones.
Since it is impossible to get any idea of their real and actual cost for a matter of about a year, provision must be made against the need for renewal, and for a time the expenditure must be estimated. At the. end of a year the estimate may be checked against the actual, and an amount put to the credit or debit side of the account as the case may be.
Why the Average of Tyre ,Mileages is Taken.
The mileage which tyres will run has always been a source of argument and controversy, more fierce than that concerning petrol or coal consumption. Constant readers will remember how, immediately after the last tables of running costs were published, in the 1923 Outlook Number of this journal, letters came to tho Editor, and were published by him in the As regards solid tyres, they were, before the war, guaranteed for 10,000 miles, which made the estimate of their cost a matter of arithmetic only. That was, indeed, the intention of the guarantee which was instituted, in the first place, to
instil confidence into the user, and make him feel that, no matter how ill his tyres behaved, his expenditure was a known and fixed amount. When solid tyres became so good, and when their quality was realized, then the guarantee was withdrawn : the necessity for it no longer existed. Now, prewar experience showed that, although in London and in favourable circumstances, the guaranteed mileage was usually exceeded, in the provinces, and where the going was none too good, the reverse was frequently the case. Consequently, -when making any estimate of costs, in which the inferior must always have more attention than the superior, a mileage of 8,00 per tyre was taken. That was the mileage basis on which the last table of costs was computed.
The Regular Exceeding of the Average.
I have lately been making certain investigations into the mileage of tyres of the quality we are now getting, and have no hesitation in saying that the average is now almost invariably exceeded. It is a common thing for a fleet of vehicles, running over roads which are none too good, to average 16,000 miles on solid tyres before they need be renewed. A mileage of 12,000 per tyre is usual, and it is rare indeed for tyres to have to be renewed at 10,000 miles. I think the reader who exercises ordinary care in driving, and who takes reasonable precautions to keep flints and stones from his tyres, and especially•from between twins, may reckon on 12,000 miles for his solids. That is to say, a set of tyres costing 150 will involve him in only a penny a mile. He may estimate the cost per mile for solid tyres by dividing. the cost, reduced to pence, by 12,000. In the case of a set which costs £30, for example, his outlay for tyres will be 30 X 240 12,000, which is 0.6d_ per mile.
As regards pneumatics, the element of luck enters so largely into the question that a much more conservative estimate of their probable life has to be made. One man may run his tyres right down to the canvas, and obtain a phenomenal mileage with them never having so much as a puncture. Another get;. a, horse-shoe into the wall the very first time he goes out, which inflicts an inj.ery from which it never really recovers. The effects of careless treatment, too, are more real and lasting with pneumatics than with solids, especially in the case of those heavier types of vehicle in which twin pneumatics are used'. A flint between a pair of pneumatics may. do a tremendous amount of harm, while, on the other hand, daily examination and removal of stones and other foreign matter from covers may add as much as 30 per cent. to their life.
A fair basis for estimating the life of the ordinary type of pneumatic, in sizes up to about 7 ins. diameter (that is to say, in all those sizes which have been in regular use for a number of years, and concerning which we have some reel and useful knowledge as to their capacities and reliability), is 5,000 miles per cover and 10,000 miles per tube. In estimating for tyres, the preliminary expenditure is generally taken as being for two good rubber non-skids and a pair of smooth tyres. The life of 5,000 miles for the covers is on the assumption that the tyres on the rear wheels are occasionally shifted to the front, and that they finish their useful life, in any ease, on the front wheels, where the work which they have to do is not so hard and where the thinner rubber coating of a part-worn tyre, or of a lighter type, is sufficient to resist all that they have to bear. Readers who have other ideas as to the beet way to select and use tyres may make their
own calculations accordingly. I do not profess to be au infallible adviser in this matter, but give my own views, which are founded on experience.
In reckoning how much his tyres ought to cost him per mile; therefore, and making the corresponding provision against renewal, the reader should take the first cost of the covers, which I will assume to be £25, and divide that by 5,000. For a £25 set, the resulting figure of cost of covers alone will be I.2d. per mile. The tubes will most likely be in the neighbourhood of 25s. apiece, and the cost of four is,. therefore, £5. That £5 will require to be spent on new tubes at-the end of 10,000 miles, BO that an amount of 0.12d. must be set apart for every mile run, for that purpose. The total amount is. therefore, 1.32d. per mile. If, in one week, a hundred miles is covered, the tyre money for that week will be its. At the end of the year, or when the first set of covers has to be renewed, the owner may checkthese figures . over against his own experience, either crediting or debiting the tyres with the difference, according to circumstances.
As regards the latest types of pneumatic tyres (those more popularly known as giants), there is no authentic information yet available aa to their probable life. The makers, it is true, aver that they are good for 10,000 miles per cover at least, and can show case where such mileages have been considerably exceeded. There are also eases—not so widely advertised—in which that mileage has required at least two sets of covers. For our purpose, that of making a preliminary estimate for eostings, to be checked later according to experdenee, the above figures of 5,0015 miles per cover will suffice.