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More Miles Per Tyre
Page 95
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By
H. Scott Hall, M.I.A.E., M.I.T.A
How to Achieve It. Figures Showing the Point at which it Pays to Install Equipment for Tyre Repairs
OF all the departments of maintenance, that relating to tyres is the one which can be made to show the maximum return for minimum outlay in labour and equipment. In cases where the normal mileage of tyres subject to casual, maintenance is 30,000 or 40,000, another operator, doing the same work in the same district, but taking proper care of his tyres, will obtain mileages of 70,000-100,000. Cases are on record of tyres which have completed well over 100,000 miles being retreaded and covering yet another 50,000 miles on the retread. The principal factors in increasing tyre wear are, as is well known, under-inflation, overloading and misalignment of wheels. 'So far as overloading is concerned. I have seen figures relating to tyres on the average-type 3-tonner habitually overloaded by 100 per cent., which showed tyre mileages ranging from 1,600 to a maximum of 1.1,000.
When Tyre Mileages Drop.
Sometimes, notwithstanding the latitude afforded by law in respect of the overall width of vehicles converted from solid to pneumatic tyres, it is impossible to fit tyres quite large enough to support the old-type heavy chassis and load. In such instances, the tyre mileage averages about 8,000, as against 40,000 in other vehicles in the same fleet adequately equipped in respect of tyre size.
So far as the effects of misalignment of wheels are conearned, corresponding figures for life are not so easy to ascertain, for the obvious reason that the wear, being particularly intensive and rapid, usually draws attention to the fault, which, more often than not, is corrected in time. As an example of the serious nature of this trouble, it may be mentioned that an excessive toe-in of i in. has an effect, in the case of a vehicle covering 480 miles per week, similar to that of dragging it bodily sideways along the road for three miles every week. Experienced operators find it worth while to check alignment once in every 3,000-5,000 miles. Tyre pressures should be checked not less frequently than once per week. Some concerns check tyre pressures daily. It is not generally realized that under-inflation, besides tending to cause damage to tyre walls through excessive flexing, is also a cause of increased expenditure in running costs in two directions. It causes the tread of the tyres to wear more quickly. The comparatively soft tyre is compressed more than would be the case if it were sufficiently inflated, there is more tread in contact with the road and, as the distorted portions of the tread tend to spring back to position as the tyre leaves the surface of the road, abrasion is increased. Additionally, this has the effect of adding to the petrol consumption per mile.
How to Lengthen Life.
Another routine maintenance operation which conduces to increased tyre life is that of a regular change of position of tyres on the vehicle. Periodically the tyres should be changed around, preferably taking care that the sequence of
. change is the same on every occasion, giving all tyres a thorough inspection, removing nails and flints, putting stopping into cuts and so on.
A measure of economy which is becoming increasingly popular with fleet owners is that of dispensing with the spare wheel, except in the ratio of, say, one spare to four vehicles. This naturally brings about a considerable economy in first cost both of spare wheels and tyres, and 19 quite practicable, certainly in respect of fleets operating within a radius of 50-60 miles.
Given reasonable care of the tyres themselves, the . prospect of trouble on the road is comparatively remote. Moreover, within the above radius of action, the odds are that any breakdown will occur within 20 miles of headquarters and it is more economical to send out a service van, with an operator and spare wheel, than to carry " dead" spares from year's end to year's end. Some operators go even farther in this connection and fit the few spare wheels that they do keep only with old repaired tyres, making provision in the maintenance organization for
the damaged tyre to be quickly repaired and the spare wheel and old tyre removed within a day.
The question as to 'the value of retreading is one which, in some quarters, is still regarded as moot. Propagandists in favour of this class of repair claim 100 per cent. more mileage at an extra cost of 50 per cent. I am of opinion that, in the majority of cases, the increased mileage is usually about 50 per cent. An important point in considering the wisdom of having this work done is to check the condition of the casing, which must be absolutely sound in every way if -retreading is to be worth while. A considerable impetus was given to the new practice of regrooving old tyres when the police commenced to interpret the regulation relating to the use of tyres which are safe to operate, as meaning that tyres must have grooves. ft has been found that regrooving the better class of tyre does add to its safety and considerably increases the braking effect. The cost of having tyres regrooved -by one of the machines specially designed for the purpose varies from 4s. to 7s.
Will Equipment Pay?
The fleet owner who is considering the installation of a tyre-repairing department must have two factors in mind —the cost of the equipment and the knowledge that if the department is to be a success, he must have an expert in charge. Efficient tyre repairing is not a matter for dabbling by amateurs. It is really the item of wages which determines the matter, for, obviously, a good man will merit good wages and unless the fleet is large enough to keep him fully occupied, that expense cannot be justified.
A first-class machine for tyre repairs will cost, without equipment, about £100, The essential accessories for handling various sizes of tyre involve a further outlay of about £25-£50. A comprehensive' plant capable of dealing with one tyre at a time and for tyres of 6-in. to 10-in.
section inclusive would cost about £300. In addition, there is the expenditure on materials for repair.
On the face of it and considering only the direct cost of the equipment in relation to the work to be done, the following figures should be useful as a guide:—A fleet of 200 vehicles, each of which is covering about 800-1,000 miles per week, will bring some 20 tyres per week to the repair shop, just about sufficient to keep one of the above machines steadily employed. It may, however, be well worth while to install such equipment for half that number of vehicles, because there are incidental economies which, in many cases, may outweigh the direct expense. If no such equipment be available, the tyres have to be sent out for repair. Taking into considers-. tion delays in transit and the time the tyres are in the repair shop, it may reasonably be expected that a week may often elapse between the dispatch of the damaged tyre and its return.
Reducing Locked-up Capital.
On the other hand, if it be repaired on the operator's premises, it can generally be put right within a few hours. What this means may, to some extent, be appreciated in relation to my statement about the use of old tyres on spare wheels. Again, these delays would involve the maintenance of a bigger stock of new tyres, the capital outlay on which would sometimes be sufficient to purchase the equipment.
Yet again, with equipment available, tyres are not °ply repaired at once and put back on the road within a minimem of time, but there is a willingness to have minor repairs attended to at once, as compared with the reluctance which is inevitable when the tyre has to be sent away and there is direct expenditure involved in paying for the repair.