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by S. G. Claydon, Express Dai ries (London) Ltd.
AN ENGINEER'S VIEW OF HOW TO MAKE USE OF TYRE RECORDS WHEN SPECIFYING TREAD PATTERNS AND PLY RATINGS
IT took legislation to create interest in tyres. Until the Road Safety Act 1967 tyres had been rather ignored by all but the few. Tyre performance was of little concern except to a relatively small number of operators and the tyre manufacturers; tyre costs were buried and only when they were compelled to do so did the operators replace them, Legislation has made it necessary for all operators—large and small—to take more than a passing interest in tyres. In some instances, however, interest is confined to ensuring that the tyres have sufficient "meat" on the crown to keep them within the law.
These extremely important components merit much more interest than they get. It is not unreasonable to suggest that operators should want to know if the tyre treads they use are those best suited for the job they are doing. Operators should be looking at mileages and consequently at costs.
To construct an accurate picture of tyre suitability and formulate a worthwhile purchasing policy, an accurate record system is essential to every road transport operator.
Rough estimates indicate that premature tyre changes by operators following the introduction of legislation cost them something like an additional 10 per cent. In a number of other cases changes to new tyres were unnecessary since the casings which were being removed could have been recut. it is claimed that recut tyres improve the normal life of the casing by about 5 per cent. This claim itself surely justifies keeping records to prove its accuracy.
I cannot think of any other vehicle component which offers such a wide variety of makes and models as does the tyre. However, generally speaking tyres fall into two main categories—radial ply and cross ply-the construction of which were dealt with in CM last week. Before operators make a choice of ply construction, it is essential that they look at the use at which the tyre has to be put. This same rule must be applied when considering the next essential in tyre purchase, that of tread pattern.
In my experience radial ply tyres are susceptible to side wall fracture and consequently I would be disinclined to use them on vehicles where there was high possibility of kerbing. It could be argued that kerbing is an element of bad driving. This may be so but it is an accepted element and tyre manufacturers build tyres with a kerbing strip built into the side wall. These are more generally built) On cross-ply tyres.
First choice
Where kerbing damage is not a consideration, radial-ply tyres would be my first choice. Records show that they give greater mileage and cost less per mile to operate although initially they are dearer. But vehicle operation does not always fail into such distinct departments and often a vehicle will be used on mixed work. This would involve high mileages over long distances and also shop deliveries where kerbing would be an element in the operation. It is, therefore, essential that tyre records should be kept to assist the operator to purchase the most suitable tyre at replacement time.
To be useful any record must be comprehensive and tyre records should show size, ply ratings, date of fitting, mileage, date of removal and reason for removal, make and tread pattern. The record should commence as soon as the tyre is fitted, or in the case of original equipment immediately the operator takes delivery of the vehicle.
Few operators specify a particular tyre as original equipment and experience shows reluctance on the part of manufacturers to depart from standard equipment. Only the largest operators can stand out for freedom of choice. This apathy by the operator or the reluctance of the manufacturer makes comparison between tread patterns difficult if not impossible. The experience so necessary to operators so that they can formulate a sensible tyre purchasing policy, is consequently denied them.
Wise course
There is, however, a course open to the operator. Tyre distributors, if approached, are often prepared to change the original equipment for a specific tyre provided this is done when the vehicle is delivered and certainly before it goes into service. I have found the charge for this type of service is relatively small when expressed in the terms of cost per mile. Tyre selection should never be left to chance and the tyre industry is in the main ready to advise on tread patterns. Provided the tyre man has full knowledge of the work on which the vehicle has to be engaged, than he can usually produce a pattern to meet the needs. Using this knowledge takes a lot of the costly guesswork out of tyre purchasing.
Having purchased a set of tyres, it is essential to see that they are correctly fitted—and here again the tyre industry has shown itself to be willing. Although large discounts are attractive, it is advisable to consider whether or not one should forgo one or two per cent of the oiscount and accept a fitting service in lieu. There must be no element of chance in tyre fitting, as this is both dangerous and costly. Records which are used to draw comparisons must show like for like and care must be taken to ensure that casings have been used on different vehicles under comparable conditions. In fact the only different element for ideal comparison would be the driver.
Just as it is essential to purchase and fit the correct tyre, so is it imperative that once fitted the tyres should be properly maintained. Regular inspection of casings, the removal of foreign bodies from between twin rears and daily checks to ensure that tyre pressures are maintained at the proper level are essential elements in tyre care. Similarly, alignment tracking and wheel fitment should be factors in vehicle inspection and maintenance.
Given proper selection, care by the driver, and attention from the workshop staff there is no reason why a cover should not attain the life expected of it by the manufacturer. This point was well made by Mr. Alex Templeton in Commercial Motor last week. At the end of the day it is the cost which counts, and in tyres this is expressed in terms of cost per mile. Therefore, to the tyres record must be added the cost of the tyre and deducted from that is scrap value.
It is here that we return to the record card because all of the information required to produce a cost is contained on that document. Keeping records in itself is an overhead and therefore it should be as simple as possible and the information it supplies must be of some use.
In sophisticated accountancy systems tyre costs records require to be fitted in to a company's overall methods and one cannot be dogmatic and state that there are only a few systems which are suitable. Provided the end product is accurate, then the method of achieving it is a matter of individual selection.
I have found the two-card system of tyre records the most favourable. This system uses one card for each tyre and a master card for each vehicle. ft will be readily appreciated. that the tyre card gives a cost per mile for the tyre while the vehicle card gives the total tyre costs for the entire life of the vehicle. By this method, the life of the tyre can be readily traced.
A tyre need not necessarily be fitted to the same vehicle throughout its life. For example, when new the casing may be used on longdistance high-speed vehicles and later removed, remoulded and fitted to a semi-trailer, local delivery vehicles or shunting vehicle. Consequently it is essential that a card should be raised for each tyre.
Operators using one or two vehicles are unlikely to have the time to introduce the two-card tyre system and in fact it would be unnecessary. A vehicle record sheet for each vehicle showing the total cost of the set of tyres in one column, the monthly mileage in another column, and the tread depth each month in a third column will provide sufficient information to show the cost per mile. Without doubt the tyre industry offers an excellent service to its customers, and in addition to the physical aspects of tyres a number of manufacturers have record systems which they make available. Tyres can no longer be ignored. Worn casings attract the attention of the law, and badly selected equipment inflates operating costs. It is just as important to keep a record of tyre performance as it is to know the mpg.