CHAPTER XXX

SOME OTHER HOT-WEATHER TIPS

There are a number of other points which should be borne in mind by auto owners with the coming of hot weather, if the most efficient service is to be had from the car.

One of the Y. M. C. A. secretaries excitedly called the school to ask why a seemingly good tire should blow out after a short run. A few minutes later another secretary put the same inquiry with variations. That is, he had a tire which was rather old, but it had been inflated for two weeks and had been running every day since inflation, when it tested eighty pounds’ pressure. It had blown out.

The first secretary had been invited by a friend to take a ride. He had watched the tires inflated and all other bits of preparedness and saw that nothing was overlooked, and settled down for a fine ride. The blow-out came about five miles away.

The trouble with both was that they had not taken into account the fact that summer was at hand. Experienced drivers know that in hot weather, whether it is according to rules or not, it is better not to keep the tire pressure so high as during the cold months, even though it means more wear on the tires.

Considerable heat is generated by rolling a tire over the ground. This heat expands the air in the tire and increases the pressure. In the winter this heat is absorbed to a large extent by the cold atmosphere and the cold and wet pavements, and therefore the pressure does not vary so much. In the summer the roads are very hot, the air temperature is high, and the heat generated by friction is not carried off to any appreciable extent.

On a recent summer trip the writer noticed that the car was riding harder than usual and a test of the pressure on the tires developed the fact that it was above normal. To find out just what the difference in pressure would be, the pressure for each tire was taken before leaving the garage next morning. After rolling about forty miles at an average speed of thirty miles an hour, the pressure was again tested. It had increased about twelve pounds on each tire.

Several tire manufacturers insist that owners shall not carry less pressure on tires in hot weather, saying that the increased pressure due to heat is not sufficient to materially affect their make. This probably is true for new tires, or for about two-thirds of their guaranteed life, but if the tire has been weakened, through having been run under-inflated, or from fabric deterioration through cuts in the tread, there is danger from the increase in pressure due to heat.

_More tires are damaged by under-inflation than by over-inflation_, because the former breaks down the side walls through running flat, in practically every case, while the over-inflation causes a blow-out only when the tire is weak at some point. It would be good practice, however, on hot summer days, to leave the garage with the tire pressure about ten pounds less than that specified by the manufacturer as being correct for his make. Any driver ought to test out his tires after running at a good clip on a hot day and find out just what they do. A little persistence would enable him to understand how much his tires heat up and he could regulate the pressure accordingly.

Manufacturers of high-pressure tires resent the above advice and declare that it is wrong. The succeeding chapter tells of definite tests made and the owner can draw his own inferences and decide for himself whether he wants _high_ tire mileage, or comfort with _pretty good_ tire mileage.

There are some other hot-weather points which it might be well to keep in mind if one would get the best results from the car. One of these is the care of the carburetor. It will be found usually that not quite so much gasoline is required as in cold weather, and therefore the dash adjustment may be carried a little nearer the lean, or air, side. This not only saves gasoline, but increases the power of the motor, for a too heavy mixture makes it run logy.

It will be found also that in most cases the hot-air stove of the carburetor may be dispensed with or adjusted. Usually provision is made on the hot-air stoves for allowing some cold air to enter, or to take cold air entirely. Where the carburetor is water-jacketed, there usually is a valve that may be closed to prevent the flow of hot water. Experiment will determine whether it is advisable to cut out the heat entirely on the individual carburetor, since all are not benefited by the change.

The water in the storage battery will evaporate more quickly in hot weather and where it has been necessary to replenish it once in two weeks in the winter, it will need to be done every week in hot weather. This is not entirely due to evaporation from heat but is accounted for in part by the fact that the engine starts easier and therefore less current is used for starting; also there is more daylight and the lamps are used less. Therefore the battery is more often in a fully charged condition, and in this condition the charging current causes more gas than when the battery is lower. This is due to the chemical action which decomposes the water, the hydrogen and oxygen gases passing off through the vent holes; the water escapes from this cause as gas and not as vapor, as it does when there is evaporation.

In hot weather city streets are generally sprinkled regularly and the country roads are oiled some time during the season. The novice going behind a street sprinkler, or reaching an oiled stretch of road, should exercise particular care to prevent skidding, as he would be unlikely to realize the danger unless he has experienced it once. This is explained fully in the part of this book devoted to skidding.

Hot weather softens grease, so that trouble may be experienced through grease or oil seeping out of transmission or differential cases, or from the grease cups. Many manufacturers recommend a heavier grease for summer than for winter to give the greatest efficiency. This softening of the grease is likely to make a little ring of grease around each cup, which will collect dust and give the car an unkempt appearance, besides there is the possibility of some of the dust working into the bearing. Grease cups must be kept turned down so that the dust is forced out, and then it should be carefully wiped off.

Every bearing needs additional care to keep dust out and lubricant in, but every moment spent in this way pays dividends in expense saved and comfort and freedom from annoyance on the road, so that the owner will do well to take note that hot weather calls for added care and precautions.