# How To Assess Your Tyre Costs

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It Pays to Make a Close Analysis of Tyre Costs on an Average Basis

HOW many small operators realize "that a journey of, say, 200 miles on a 3-tonner involves a tyre cost of eight to ten shillings? How many include this figure when quoting for work? Petrol, oil, and time are reckoned, and "a bit for wear and tear,but far too frequently the last-mentioned is quite inadequate. Only by closely analysing the various costs can a correct estimate be obtained.

Let us suppose that a 3-tanner, fitted with 32 by 6 heavy-duty tyres, is travelling frorn London to Birmingham and back, a distance of approximately 220 miles. If we assume that the tyres have cost about £7 each (242 the set of six), and that they give a mileage of 20,0(X), this is equivalent to a total tyre cost of 231 miles per shilling. Thus, the journey costs 9s. 3d. in tyres alone.

Most people will agree, I think, that the figures on which this calculation is based are quite fair. If cheaper tyres of inferior performance be used, the proportions are still the same.

Not a Hit-or-miss Business.

The admirable articles of "S.T.R..' have established the. fact that costing need not be a hit-or-miss business, and it was with a similar idea in mind that 1 suggested a layout for a tyre cost and maintenance chart as published some time back in this journal.

The main purpose of the chart, however, was to help operators to determine the best tyre value, rather than to help them to work out a basis of tyre costs on which to form their quotations for work. But two birds can be killed with a single stone.

To get down to exact figures, it is necessary to work out the average mileage cost. This can be obtained from the aforementioned chart, but it must not be forgotten that the

average figure is important. You may get a normal Mileage of 20,000

from a set of tyres, but if one of these fails prematurely, and a new tyre has to be purchased, the average drops considerably.

Here is an example: A set of six tyres costing £5 each gives a normal mileage of, say, 20,000. This is equivalent to 666 miles per pound. But, supposing that one tyre bursts after a short period of service. Another tyre costing £5 is bought, but the original total of approximately 20,000 still holds. This brings down our figure to 571 miles per pound.

Premature Bursts.

In these days of overloading it is not unusual to hear of two tyres, out of a set of six, bursting prematurely. Our average mileage would then be reduced to 500.

All this may seem obvious and unnecessary, but it is mentioned in order to bring home the fact that there is a vast difference between normal mileage and average mileage; too many operators are apt to forget the tyres which fail.

If a tyre fail and be replaced at a special price under the makers' guarantee, the average mileage cost is not affected, for the simple reason that the new tyre is replaced at a price which is in proportion to the mileage which the burst tyre has given.

In other words, if a tyre costing £8 bursts when only a quarter worn, the operator has had only 30s. worth of wear from it. The manufacturer, if the burst be due to any manufacturing defect, will replace it for 30s. If the replacement tyre gives a normal mileage, the operator has not lost a penny on the transaction—at least, so far as the actual tyre is concerned. However, incidental expenses attendant on burst tyres must be taken into account.

Now let us go back to the chart. For our present purpose, the details we require are the cost of the tyre and its mileage yield. It will be remembered that the cost in pounds was divided into the total mileage, thus giving the number of miles per pound sterling. This is the only guide to tyre value.

It is necessary to treat each vehicle separately, unless they are all of the same type, for there are great variations between different lorries, not only in tyre mileage but also in tyre cost.

Moreover, we want to know the mileage cost on each particular vehicle, so that we can quote accurately for any job which it may be called upon to do. It is useless to lump together the figures of a 2-tonner with those of a 4-tanner.

Thus, we add together the total resultant mileages from all tyres on each individual lorry, not forgetting to include the good and the bad. We divide this by the total cost, in pounds, of the tyres and, thereby, arrive at the mileage per pound per tyre.

Tyre Miles per Pound of Rubber.

If the vehicle has six wheels, we divide this mileage by six (or by four, if it be a four-wheeler). The answer is the number of vehicle tyre miles we can obtain per pound. If desired, it is easy to work out the cost per mile on the same basis.

It is worth working out. I feel sure that nine fleet owners out of ten will get a bad shock when they realize to what extent their ideas of cost-per-mile have been at fault. It is easy to drop into the habit of assuming that the tyre cost per journey is negligible, but when this is put in figures it will be seen immediately that the "little bit for wear and tear" is hopelessly inadequate.

L.V.B.