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.