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CHOOSIN !YRES
than simply buying a well
make that fits
By R. DI CATER A M Inst B E CNOOSING tyres can be a frustrating business, especially if one does not first of all decide exactly what is wanted. In my opinion three points should be borne in mind when comparing the merits of one make with another. The first (and I consider this to be the most important for the small operator) centres on the after-sales service that will be available with the make that is decided upon. The second is the suitability of the cover to accept a minimum of one remould and to give a useful first-life —on, say, a rigid eight-wheeler—of around 50,000 miles. Finally, there is the cost.
It is a fact that whatever make of tyre is bought a comparable cover will cost an identical amount of money. However, depending on the company that it is bought through, rather than from, it is possible to obtain a discount allowed against the amount of business done to what amounts, in some cases, to a ridiculous level.
I have known cases where operators have complained bitterly at the service that has been given them when in trouble, only to discover, subsequently, that they have squeezed the last 4per cent discount out of their supplier, leaving him no margin with which to supply after-sales service. It is extremely important that the overall picture should be ascertained when deciding to purchase a particular brand and, as with most other items entailing capital outlay and service costs, the capital outlay can often prove to be the least of one's worries. A few shillings saved on initial cost is of little importance when a vehicle is stuck somewhere with a blowout and no service.
Be Shrewd
With regard to assessing the capability of a certain make of tyre, I believe this can be done only by shrewd, practical experience. The sales talk of the tyre representative can be largely discounted if he does not enjoy your business, although it is fair to say that usually there is more information available from the people you are not dealing with than from those with whom you are.
If you have been persuaded to change your chosen make of tyre. then first try a set on a vehicle known to be particularly heavy on tyres, or on a route which has proved to be expensive to operate with regard to tyre life. If normal procedure is strict with regard to tyre servicing, then the same sequence of operations must be followed to secure a relative picture. Conversely, if the tyres normally do not get much attention, then to carefully look after a test set will reveal nothing. Another important point is the effect that a driver will have on tyre life, so the results must be compared with a similar set obtained, if possible, with the same vehicle, on the same route, with the same (Irk er.
When collating the results of a test it is important that the average mileage run, the number of tyres used in the test that were found suitable for remoulding and any other factors shown up during the test, are taken into consideration. For instance, it is useless taking any one tyre that has done 100,000 miles when there may have been three others of the same set which have not reached the 50,000mile mark. It is important to work on average performance against average performance. In deciding on the tyres that will successfully stand remoulding, those that have been accidentally damaged must be discounted and the decision made from the success or otherwise of covers that have been through the remoulding process. Usually this can be judged by the incidents that occur during the remould's life—such things as separation, blowing out, chaffing and unusually short tread life being points to watch for.
Seasonal Results Differ
Whilst on the subject of tyre life, it is almost impossible to expect results from two tests carried out at different seasons of. the year to provide any useful data from which you can decide to use a certain type or make. It must be
remembered that ambient temperatures, road surface conditions, traffic conditions and even the temperanient of the driver change with the seasons. Therefore, if it is possible to equip two identical vehicles, operating on the same route, with two different makes of tyre and swopping drivers on alternate days, an accurate and extremely quick assessment of performance can be obtained—and I suggest that if this can be arranged it is by far the most satisfactory method.
Other points which arise when assessing the suitability of a tyre for a particular use are perhaps not so evident at first. I can remember an incident when the driver of a vehicle with a single-drive rear bogie complained bitterly of losing traction when the roads were wet. 'File subsequent fitting of a type of tyre which was not recommended by any of the experts resulted in excellent tyre mileage figures from the vehicle in question and never a subsequent complaint from the driver. Personally. 1 do not think that it made a scrap of difference to the traction: but the end results were good and that, after all, is what matters.
Another test carried out with a weli-known tyre resulted in first-class mileage results, but it produced such a crop of steering complaints that the tyres were immediately discarded.
Yet another test, this time of a new type of tread, produced such an unusual wear pattern that the vehicle fitted with the test tyres was continually being brought into the garage to have the steering alignment checked. Inevitably the drivers became suspicious of the tyre, with the result that it received the worst treatment possible andwas subsequently discarded.
Maintenance Will Pay Ii is true to say that a certain type of tyre suits a particular vehicle or job, cir even a driver, better than others, and this is the whole key to obtaining the best performance from your equipment. An efficient tyre maintenance system and a sensible choice of initial equipment—that is to say not underestimating the size or ply rating that will be needed to carry your loads—will certainly pay dr.
The merits or otherwise of the various types of construction that are offered by the different companies can have considerable bearing on tyre performance. These
CHOOSING TYRES
This section o, the Firestone Technical Data manual shows in column 9 (approximate revs per mile) one of the most important reasons for pairing tyres. be seen that the static loaded radius is not the only controlling factor, clearly showing. that it is not enough ta select just a tyre size. (See units marked with on asterisk).
points are covered more fully by my colleague, Tony Wilding, elsewhere in this issue. But it. has been my experience that whilst guidance can be obtained from the makers it is not wise to accept a change without first being satisfied as to the subsequent results. As I said earlier, my first requirement when contemplating a change in any of the equipment that has direct effects on the operational reliability of a fleet is: " How quickly will the supplying organization get me out of trouble should I be unfortunate enough to get into it?"
An important part of the business of choosing tyres is that of keeping tyre history records. From these it is possible to see what the cost of running each make and type in one's fleet is. and when coupled with the rest of the fleet history records one can quickly isolate a particular case for purchasing, or not purchasing a particular unit.
It will not be until about 12 to 18 months after the purchase of a batch of tyres that a picture will begin to emerge from the records, and during that time if is quite possible that the maker will change the specification of the type one is using. Therefore, it is essential that the keeping of tyre records is not allowed to become .a largescale, tedious and expensive operation which can soon develop into a monster that will devour more cash than it will save.
Keep records simpie
An instance of sensible record keeping was shown to me recently when I visited one of the country's largest C-licensed operators, Although this company has large numbers of vehicles which are controlled by a number of different area engineers, only one area keeps tyre history records. These are then made available to all other areas who can—as the company's system of operation is standard throughout—get the required picture.
It will he seen that this avoids the costly duplication of recording. The records that the company does keep show the person responsible for deciding what to buy. the cost per mile of operation, he failure rate (if any) and the number of claims that have been judged by the tyre panel as being valid. Accident damage sustained is not counted as a tyre fault, Probably the most useful figure obtained is the cost per mile, as the performance of a cover obviously shows up in this immediately.
Cross reference to the vehicle record sheets, which of course bear the same milometer readings for a given date as the tyre records, quickly shows up any difference in the performance of a vehicle when a new type of tyre is fitted.
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This also is taken -nto consideration when the company makes its choice on the next occasion.
A point made by the engineer to whom I spoke during this visit was that he placed a lot of faith in the fact that tyre companies were responsible to him for carrying out routine inspections. This had a sharper effect on depot managers with regard to proper tyre maintenance than if an employee of the company'did the job., He emphasized that strict attention to tyre pressures was largely responsible for the excellent results that were achieved, but also said that it was not possible to guarantee the life of any tyre; it was a prOblem that must be Continually watched. He also considered it was 'essential that all tyres removed from vehicles Were returned to a central depot, to allow inspection by a person who could keep an overall picture in his mind regarding the tyre performances being achieved in outlying depots.
Watch had practices As tyres represent a major item in running costs of a vehicle, it is essential that close checks are kept on such points as the state at the time of removal, whether • drivers in a particular depot are being allowed to continually damage covers (through kerbing, for instance) and the degree, of efficiency with regard to axle and steering alignment that the depot keeps. Any of these points will quickly show up as being normal practice and can just as quickly be stainped out.
To sum up, unless one's fleet is so large that it requires a department to deal only with tyres, keep the record system simple so that the cost of running it is an economical proposition. Do not keep records that are so detailed that only a' very small part of them will ever See daylight' once 'they are completed. Unless there is an extremely good reason do not change the chosen make. Changing for the sake of changing can prove both disappointing and expensive. Do not rely on the experience • Of others as -a -guide to what to buy unless their vehicles are the same • as your own, they carry out the same sort of business, and they operate in the same area.. It is wise not to put all the eggs in one -..basket;. remember. that a hit of competition is still the best way to keep suppliers on their toes.
Finally, do not underestimate What you need to do your job. And when you have decided, work your choice at a fair level. Bad maintenance and overloading can only reduce the life of tyre equipment. and there have been many instances of vehicles being completely written off through a failure.